Now, i'll explain and show the INVITE causing the crash:
The INVITE packet is fragmented in two frames. The capture is done with the ethereal (wireshark now) and it's the next:

***********************************************************************
No.     Time        Source                Destination           Protocol Info
      1 0.000000    2001:720:1500:24:fcfd:ff:fe0d:101 2001:720:1500:1b:20c:76ff:fe6c:4658 IPv6     IPv6 fragment (nxt=UDP (0x11) off=1408 id=0x5)

Frame 1 (431 bytes on wire, 431 bytes captured)
    Arrival Time: Nov 30, 2006 16:40:02.345512000
    Time delta from previous packet: 0.000000000 seconds
    Time since reference or first frame: 0.000000000 seconds
    Frame Number: 1
    Packet Length: 431 bytes
    Capture Length: 431 bytes
    Protocols in frame: sll:ipv6:data
Linux cooked capture
    Packet type: Unicast to another host (3)
    Link-layer address type: 1
    Link-layer address length: 6
    Source: Cisco_17:28:70 (00:d0:06:17:28:70)
    Protocol: IPv6 (0x86dd)
Internet Protocol Version 6
    Version: 6
    Traffic class: 0x00
    Flowlabel: 0x00000
    Payload length: 375
    Next header: IPv6 fragment (0x2c)
    Hop limit: 61
    Source address: 2001:720:1500:24:fcfd:ff:fe0d:101 (2001:720:1500:24:fcfd:ff:fe0d:101)
    Destination address: 2001:720:1500:1b:20c:76ff:fe6c:4658 (2001:720:1500:1b:20c:76ff:fe6c:4658)
Fragmentation Header
    Next header: UDP (0x11)
    Offset: 1408
    More fragments: No
    Identification: 0x00000005
Data (367 bytes)

0000  00 03 00 01 00 06 00 d0 06 17 28 70 00 00 86 dd   ..........(p....
0010  60 00 00 00 01 77 2c 3d 20 01 07 20 15 00 00 24   `....w,= .. ...$
0020  fc fd 00 ff fe 0d 01 01 20 01 07 20 15 00 00 1b   ........ .. ....
0030  02 0c 76 ff fe 6c 46 58 11 00 05 80 00 00 00 05   ..v..lFX........
0040  50 44 41 54 45 0d 0a 52 65 70 6c 61 63 65 73 3a   PDATE..Replaces:
0050  20 64 34 63 38 37 63 39 30 32 64 31 62 35 32 62    d4c87c902d1b52b
0060  32 38 36 62 61 64 39 36 66 33 63 62 62 36 31 34   286bad96f3cbb614
0070  34 40 5b 32 30 30 31 3a 37 32 30 3a 31 35 30 30   4@[2001:720:1500
0080  3a 31 61 3a 32 33 30 3a 31 62 66 66 3a 66 65 31   :1a:230:1bff:fe1
0090  30 3a 35 66 62 33 5d 3b 72 65 61 73 6f 6e 3d 53   0:5fb3];reason=S
00a0  49 50 20 72 6f 75 74 65 20 68 61 73 20 63 68 61   IP route has cha
00b0  6e 67 65 64 0d 0a 43 6f 6e 74 65 6e 74 2d 54 79   nged..Content-Ty
00c0  70 65 3a 20 61 70 70 6c 69 63 61 74 69 6f 6e 2f   pe: application/
00d0  73 64 70 0d 0a 43 6f 6e 74 65 6e 74 2d 4c 65 6e   sdp..Content-Len
00e0  67 74 68 3a 20 31 39 35 0d 0a 0d 0a 76 3d 30 0d   gth: 195....v=0.
00f0  0a 6f 3d 69 73 61 62 65 6c 20 30 20 30 20 49 4e   .o=isabel 0 0 IN
0100  20 49 50 36 20 5b 32 30 30 31 3a 37 32 30 3a 31    IP6 [2001:720:1
0110  35 30 30 3a 31 61 3a 32 33 30 3a 31 62 66 66 3a   500:1a:230:1bff:
0120  66 65 31 30 3a 35 66 62 33 5d 0d 0a 73 3d 2d 0d   fe10:5fb3]..s=-.
0130  0a 63 3d 49 4e 20 49 50 36 20 32 30 30 31 3a 37   .c=IN IP6 2001:7
0140  32 30 3a 31 35 30 30 3a 31 61 3a 32 33 30 3a 31   20:1500:1a:230:1
0150  62 66 66 3a 66 65 31 30 3a 35 66 62 33 0d 0a 74   bff:fe10:5fb3..t
0160  3d 30 20 30 0d 0a 6d 3d 61 75 64 69 6f 20 32 32   =0 0..m=audio 22
0170  32 32 34 20 52 54 50 2f 41 56 50 20 30 20 33 20   224 RTP/AVP 0 3
0180  34 20 35 20 36 20 38 20 31 35 20 31 38 0d 0a 6d   4 5 6 8 15 18..m
0190  3d 76 69 64 65 6f 20 32 32 32 32 32 20 52 54 50   =video 22222 RTP
01a0  2f 41 56 50 20 32 36 20 33 34 20 33 31 0d 0a      /AVP 26 34 31..
No.     Time        Source                Destination           Protocol Info
      2 0.000117    2001:720:1500:24:fcfd:ff:fe0d:101 2001:720:1500:1b:20c:76ff:fe6c:4658 SIP      Request: INVITE sip:[2001:720:1500:1b:20c:76ff:fe6c:4658]:5060;transport=udp

Frame 2 (1512 bytes on wire, 1512 bytes captured)
    Arrival Time: Nov 30, 2006 16:40:02.345629000
    Time delta from previous packet: 0.000117000 seconds
    Time since reference or first frame: 0.000117000 seconds
    Frame Number: 2
    Packet Length: 1512 bytes
    Capture Length: 1512 bytes
    Protocols in frame: sll:ipv6:ipv6:udp:sip
Linux cooked capture
    Packet type: Sent by us (4)
    Link-layer address type: 1
    Link-layer address length: 6
    Source: fe:fd:00:0c:00:01 (fe:fd:00:0c:00:01)
    Protocol: IPv6 (0x86dd)
Internet Protocol Version 6
    Version: 6
    Traffic class: 0x00
    Flowlabel: 0x00000
    Payload length: 1456
    Next header: IPv6 (0x29)
    Hop limit: 64
    Source address: 2001:720:1500:1b:fcfd:ff:fe0c:1 (2001:720:1500:1b:fcfd:ff:fe0c:1)
    Destination address: 2001:720:1500:24:20c:76ff:fe6c:4658 (2001:720:1500:24:20c:76ff:fe6c:4658)
Internet Protocol Version 6
    Version: 6
    Traffic class: 0x00
    Flowlabel: 0x00000
    Payload length: 1416
    Next header: IPv6 fragment (0x2c)
    Hop limit: 60
    Source address: 2001:720:1500:24:fcfd:ff:fe0d:101 (2001:720:1500:24:fcfd:ff:fe0d:101)
    Destination address: 2001:720:1500:1b:20c:76ff:fe6c:4658 (2001:720:1500:1b:20c:76ff:fe6c:4658)
Fragmentation Header
    Next header: UDP (0x11)
    Offset: 0
    More fragments: Yes
    Identification: 0x00000005
User Datagram Protocol, Src Port: sip (5060), Dst Port: sip (5060)
    Source port: sip (5060)
    Destination port: sip (5060)
    Length: 1775
    Checksum: 0x9301
Session Initiation Protocol
    Request-Line: INVITE sip:[2001:720:1500:1b:20c:76ff:fe6c:4658]:5060;transport=udp SIP/2.0
        Method: INVITE
        Resent Packet: False
    Message Header
        Record-Route: <sip:[2001:720:1500:24:FCFD:FF:FE0D:101];ftag=12122347;lr=on>
        Record-Route: <sip:[2001:720:1500:1B:FCFD:FF:FE0C:103];ftag=12122347;lr=on>
        Record-Route: <sip:[2001:720:1500:1A:FCFD:FF:FE0A:103];ftag=12122347;lr=on>
        Record-Route: <sip:[2001:720:1500:19:FCFD:FF:FE0E:101];ftag=12122347;lr=on>
        Call-ID: 138104335821ad9b21971c7d6059b6c8@[2001:720:1500:1a:230:1bff:fe10:5fb3]
        CSeq: 1 INVITE
        From: "ueA" <sip:ueA@domainA.ammi.dit.upm.es>;tag=12122347
            SIP Display info: "ueA"
            SIP from address: sip:ueA@domainA.ammi.dit.upm.es
            SIP tag: 12122347
        To: <sip:ueC@domainC.ammi.dit.upm.es>
            SIP to address: sip:ueC@domainC.ammi.dit.upm.es
        Via: SIP/2.0/UDP [2001:720:1500:24:FCFD:FF:FE0D:101];branch=z9hG4bK1205.ddbf87e4.0
        Via: SIP/2.0/UDP [2001:720:1500:1B:FCFD:FF:FE0C:103];branch=z9hG4bK1205.c8a66626.0
        Via: SIP/2.0/UDP [2001:720:1500:1B:FCFD:FF:FE0C:102];branch=z9hG4bK1205.1cb3a0b4.0
        Via: SIP/2.0/UDP [2001:720:1500:1A:FCFD:FF:FE0A:103];branch=z9hG4bK1205.44344f04.0
        Via: SIP/2.0/UDP [2001:720:1500:19:FCFD:FF:FE0E:101];branch=z9hG4bK1205.a44e3b34.0
        Via: SIP/2.0/UDP [2001:720:1500:1a:230:1bff:fe10:5fb3]:61052;branch=z9hG4bK40e1844512a234e326ef8222f8b204fb
        Max-Forwards: 12
        Contact: "ueA" <sip:[2001:720:1500:1a:230:1bff:fe10:5fb3]:61052;transport=udp>
            Contact Binding: "ueA" <sip:[2001:720:1500:1a:230:1bff:fe10:5fb3]:61052;transport=udp>
                URI: "ueA" <sip:[2001:720:1500:1a:230:1bff:fe10:5fb3]:61052;transport=udp>
                    SIP Display info: "ueA"
                    SIP contact address: sip:[2001:720:1500:1a:230:1bff:fe10:5fb3]:61052
        P-Preferred-Identity: "ueA" <sip:ueA@domainA.ammi.dit.upm.es>;tag=12122347
        Privacy: none
        P-Access-Network-Info: 3GPP-UTRAN-TDD;utran-cell-id-3gpp=181086
        Allow: INVITE,ACK,CANCEL,BYE,PRACK,U

0000  00 04 00 01 00 06 fe fd 00 0c 00 01 00 00 86 dd   ................
0010  60 00 00 00 05 b0 29 40 20 01 07 20 15 00 00 1b   `.....)@ .. ....
0020  fc fd 00 ff fe 0c 00 01 20 01 07 20 15 00 00 24   ........ .. ...$
0030  02 0c 76 ff fe 6c 46 58 60 00 00 00 05 88 2c 3c   ..v..lFX`.....,<
0040  20 01 07 20 15 00 00 24 fc fd 00 ff fe 0d 01 01    .. ...$........
0050  20 01 07 20 15 00 00 1b 02 0c 76 ff fe 6c 46 58    .. ......v..lFX
0060  11 00 00 01 00 00 00 05 13 c4 13 c4 06 ef 93 01   ................
0070  49 4e 56 49 54 45 20 73 69 70 3a 5b 32 30 30 31   INVITE sip:[2001
0080  3a 37 32 30 3a 31 35 30 30 3a 31 62 3a 32 30 63   :720:1500:1b:20c
0090  3a 37 36 66 66 3a 66 65 36 63 3a 34 36 35 38 5d   :76ff:fe6c:4658]
00a0  3a 35 30 36 30 3b 74 72 61 6e 73 70 6f 72 74 3d   :5060;transport=
00b0  75 64 70 20 53 49 50 2f 32 2e 30 0d 0a 52 65 63   udp SIP/2.0..Rec
00c0  6f 72 64 2d 52 6f 75 74 65 3a 20 3c 73 69 70 3a   ord-Route: <sip:
00d0  5b 32 30 30 31 3a 37 32 30 3a 31 35 30 30 3a 32   [2001:720:1500:2
00e0  34 3a 46 43 46 44 3a 46 46 3a 46 45 30 44 3a 31   4:FCFD:FF:FE0D:1
00f0  30 31 5d 3b 66 74 61 67 3d 31 32 31 32 32 33 34   01];ftag=1212234
0100  37 3b 6c 72 3d 6f 6e 3e 0d 0a 52 65 63 6f 72 64   7;lr=on>..Record
0110  2d 52 6f 75 74 65 3a 20 3c 73 69 70 3a 5b 32 30   -Route: <sip:[20
0120  30 31 3a 37 32 30 3a 31 35 30 30 3a 31 42 3a 46   01:720:1500:1B:F
0130  43 46 44 3a 46 46 3a 46 45 30 43 3a 31 30 33 5d   CFD:FF:FE0C:103]
0140  3b 66 74 61 67 3d 31 32 31 32 32 33 34 37 3b 6c   ;ftag=12122347;l
0150  72 3d 6f 6e 3e 0d 0a 52 65 63 6f 72 64 2d 52 6f   r=on>..Record-Ro
0160  75 74 65 3a 20 3c 73 69 70 3a 5b 32 30 30 31 3a   ute: <sip:[2001:
0170  37 32 30 3a 31 35 30 30 3a 31 41 3a 46 43 46 44   720:1500:1A:FCFD
0180  3a 46 46 3a 46 45 30 41 3a 31 30 33 5d 3b 66 74   :FF:FE0A:103];ft
0190  61 67 3d 31 32 31 32 32 33 34 37 3b 6c 72 3d 6f   ag=12122347;lr=o
01a0  6e 3e 0d 0a 52 65 63 6f 72 64 2d 52 6f 75 74 65   n>..Record-Route
01b0  3a 20 3c 73 69 70 3a 5b 32 30 30 31 3a 37 32 30   : <sip:[2001:720
01c0  3a 31 35 30 30 3a 31 39 3a 46 43 46 44 3a 46 46   :1500:19:FCFD:FF
01d0  3a 46 45 30 45 3a 31 30 31 5d 3b 66 74 61 67 3d   :FE0E:101];ftag=
01e0  31 32 31 32 32 33 34 37 3b 6c 72 3d 6f 6e 3e 0d   12122347;lr=on>.
01f0  0a 43 61 6c 6c 2d 49 44 3a 20 31 33 38 31 30 34   .Call-ID: 138104
0200  33 33 35 38 32 31 61 64 39 62 32 31 39 37 31 63   335821ad9b21971c
0210  37 64 36 30 35 39 62 36 63 38 40 5b 32 30 30 31   7d6059b6c8@[2001
0220  3a 37 32 30 3a 31 35 30 30 3a 31 61 3a 32 33 30   :720:1500:1a:230
0230  3a 31 62 66 66 3a 66 65 31 30 3a 35 66 62 33 5d   :1bff:fe10:5fb3]
0240  0d 0a 43 53 65 71 3a 20 31 20 49 4e 56 49 54 45   ..CSeq: 1 INVITE
0250  0d 0a 46 72 6f 6d 3a 20 22 75 65 41 22 20 3c 73   ..From: "ueA" <s
0260  69 70 3a 75 65 41 40 64 6f 6d 61 69 6e 41 2e 61   ip:ueA@domainA.a
0270  6d 6d 69 2e 64 69 74 2e 75 70 6d 2e 65 73 3e 3b   mmi.dit.upm.es>;
0280  74 61 67 3d 31 32 31 32 32 33 34 37 0d 0a 54 6f   tag=12122347..To
0290  3a 20 3c 73 69 70 3a 75 65 43 40 64 6f 6d 61 69   : <sip:ueC@domai
02a0  6e 43 2e 61 6d 6d 69 2e 64 69 74 2e 75 70 6d 2e   nC.ammi.dit.upm.
02b0  65 73 3e 0d 0a 56 69 61 3a 20 53 49 50 2f 32 2e   es>..Via: SIP/2.
02c0  30 2f 55 44 50 20 5b 32 30 30 31 3a 37 32 30 3a   0/UDP [2001:720:
02d0  31 35 30 30 3a 32 34 3a 46 43 46 44 3a 46 46 3a   1500:24:FCFD:FF:
02e0  46 45 30 44 3a 31 30 31 5d 3b 62 72 61 6e 63 68   FE0D:101];branch
02f0  3d 7a 39 68 47 34 62 4b 31 32 30 35 2e 64 64 62   =z9hG4bK1205.ddb
0300  66 38 37 65 34 2e 30 0d 0a 56 69 61 3a 20 53 49   f87e4.0..Via: SI
0310  50 2f 32 2e 30 2f 55 44 50 20 5b 32 30 30 31 3a   P/2.0/UDP [2001:
0320  37 32 30 3a 31 35 30 30 3a 31 42 3a 46 43 46 44   720:1500:1B:FCFD
0330  3a 46 46 3a 46 45 30 43 3a 31 30 33 5d 3b 62 72   :FF:FE0C:103];br
0340  61 6e 63 68 3d 7a 39 68 47 34 62 4b 31 32 30 35   anch=z9hG4bK1205
0350  2e 63 38 61 36 36 36 32 36 2e 30 0d 0a 56 69 61   .c8a66626.0..Via
0360  3a 20 53 49 50 2f 32 2e 30 2f 55 44 50 20 5b 32   : SIP/2.0/UDP [2
0370  30 30 31 3a 37 32 30 3a 31 35 30 30 3a 31 42 3a   001:720:1500:1B:
0380  46 43 46 44 3a 46 46 3a 46 45 30 43 3a 31 30 32   FCFD:FF:FE0C:102
0390  5d 3b 62 72 61 6e 63 68 3d 7a 39 68 47 34 62 4b   ];branch=z9hG4bK
03a0  31 32 30 35 2e 31 63 62 33 61 30 62 34 2e 30 0d   1205.1cb3a0b4.0.
03b0  0a 56 69 61 3a 20 53 49 50 2f 32 2e 30 2f 55 44   .Via: SIP/2.0/UD
03c0  50 20 5b 32 30 30 31 3a 37 32 30 3a 31 35 30 30   P [2001:720:1500
03d0  3a 31 41 3a 46 43 46 44 3a 46 46 3a 46 45 30 41   :1A:FCFD:FF:FE0A
03e0  3a 31 30 33 5d 3b 62 72 61 6e 63 68 3d 7a 39 68   :103];branch=z9h
03f0  47 34 62 4b 31 32 30 35 2e 34 34 33 34 34 66 30   G4bK1205.44344f0
0400  34 2e 30 0d 0a 56 69 61 3a 20 53 49 50 2f 32 2e   4.0..Via: SIP/2.
0410  30 2f 55 44 50 20 5b 32 30 30 31 3a 37 32 30 3a   0/UDP [2001:720:
0420  31 35 30 30 3a 31 39 3a 46 43 46 44 3a 46 46 3a   1500:19:FCFD:FF:
0430  46 45 30 45 3a 31 30 31 5d 3b 62 72 61 6e 63 68   FE0E:101];branch
0440  3d 7a 39 68 47 34 62 4b 31 32 30 35 2e 61 34 34   =z9hG4bK1205.a44
0450  65 33 62 33 34 2e 30 0d 0a 56 69 61 3a 20 53 49   e3b34.0..Via: SI
0460  50 2f 32 2e 30 2f 55 44 50 20 5b 32 30 30 31 3a   P/2.0/UDP [2001:
0470  37 32 30 3a 31 35 30 30 3a 31 61 3a 32 33 30 3a   720:1500:1a:230:
0480  31 62 66 66 3a 66 65 31 30 3a 35 66 62 33 5d 3a   1bff:fe10:5fb3]:
0490  36 31 30 35 32 3b 62 72 61 6e 63 68 3d 7a 39 68   61052;branch=z9h
04a0  47 34 62 4b 34 30 65 31 38 34 34 35 31 32 61 32   G4bK40e1844512a2
04b0  33 34 65 33 32 36 65 66 38 32 32 32 66 38 62 32   34e326ef8222f8b2
04c0  30 34 66 62 0d 0a 4d 61 78 2d 46 6f 72 77 61 72   04fb..Max-Forwar
04d0  64 73 3a 20 31 32 0d 0a 43 6f 6e 74 61 63 74 3a   ds: 12..Contact:
04e0  20 22 75 65 41 22 20 3c 73 69 70 3a 5b 32 30 30    "ueA" <sip:[200
04f0  31 3a 37 32 30 3a 31 35 30 30 3a 31 61 3a 32 33   1:720:1500:1a:23
0500  30 3a 31 62 66 66 3a 66 65 31 30 3a 35 66 62 33   0:1bff:fe10:5fb3
0510  5d 3a 36 31 30 35 32 3b 74 72 61 6e 73 70 6f 72   ]:61052;transpor
0520  74 3d 75 64 70 3e 0d 0a 50 2d 50 72 65 66 65 72   t=udp>..P-Prefer
0530  72 65 64 2d 49 64 65 6e 74 69 74 79 3a 20 22 75   red-Identity: "u
0540  65 41 22 20 3c 73 69 70 3a 75 65 41 40 64 6f 6d   eA" <sip:ueA@dom
0550  61 69 6e 41 2e 61 6d 6d 69 2e 64 69 74 2e 75 70   ainA.ammi.dit.up
0560  6d 2e 65 73 3e 3b 74 61 67 3d 31 32 31 32 32 33   m.es>;tag=121223
0570  34 37 0d 0a 50 72 69 76 61 63 79 3a 20 6e 6f 6e   47..Privacy: non
0580  65 0d 0a 50 2d 41 63 63 65 73 73 2d 4e 65 74 77   e..P-Access-Netw
0590  6f 72 6b 2d 49 6e 66 6f 3a 20 33 47 50 50 2d 55   ork-Info: 3GPP-U
05a0  54 52 41 4e 2d 54 44 44 3b 75 74 72 61 6e 2d 63   TRAN-TDD;utran-c
05b0  65 6c 6c 2d 69 64 2d 33 67 70 70 3d 31 38 31 30   ell-id-3gpp=1810
05c0  38 36 0d 0a 41 6c 6c 6f 77 3a 20 49 4e 56 49 54   86..Allow: INVIT
05d0  45 2c 41 43 4b 2c 43 41 4e 43 45 4c 2c 42 59 45   E,ACK,CANCEL,BYE
05e0  2c 50 52 41 43 4b 2c 55                           ,PRACK,U

***********************************************************************
If you want the .cap file for open it with ethereal, ask it for me.

Thanks for your help.