[Serusers] SER + SEMS problem with ACK

Hello, I'm using sems with ser 0.9.7-pre6 and I have a problem with ACK, as you can see , the other part is not acceting them, what is wrong... ? just, the SIP is going via a IPSEC vpn. Thanks for your help Laurent ? 212.190.89.140 -> 212.249.14.236 ............s....Y...5..E.....@....d..Y...}9.......fSIP/2.0 486 Busy here..Via: SIP/2.0/UDP 195.129.125.57;branch=z9hG4bK8ec6.3148d226.0..From:417875185 51 <sip:+41787518551@bylltel.com>;tag=568D320F-461F45CB000A78E3-40807960..To: <sip:+41787518551@212.190.89.137>;tag=6083161C-10B1..Date: Fri, 13 Apr 2007 08:56:47 GMT..Call-ID: 5A1CFF5D-461F45CB000A78EE-40807960@212.249.14.236..Server: Cisco-SIPGateway/IOS-12.x..CSeq: 10 INVITE..Allow-Events: telephone-ev ent..Content-Length: 0.... U 212.190.89.137:5060 -> 195.129.125.57:5060 SIP/2.0 486 Busy here..Via: SIP/2.0/UDP 195.129.125.57;branch= z9hG4bK8ec6.3148d226.0..From: 41787518551 <sip:+41787518551@bylltel.com 5CB000A78E3-40807960..To: <sip:+41787518551@212.190.89.137>;tag=6083161C-10B1..Date: Fri, 13 Apr 2007 08:56:47 GMT..Call-ID: 5A1CFF5D-461F45CB000A78EE-40 807960@212.249.14.236..Server: Cisco-SIPGateway/IOS-12.x..CSeq: 10 INVITE..Allow-Events: telephone-event..Content-Length: 0.... ? 212.249.14.236 -> 212.190.89.140 ................koG.B...E.....@.@..&..}9..Y.........ACK sip:+41787518551@212.190.89.137 SIP/2.0..Via: SIP/2.0/UDP 195.129.125.57 ;branch=z9hG4bK8ec6.3148d 226.0..From: 41787518551 <sip:+41787518551@bylltel.com>;tag=568D320F-461F45CB000A78E3-40807960..Call-ID: 5A1CFF5D-461F45CB000A78EE-40807960(a)212.249.14.23 6..To: <sip:+41787518551@212.190.89.137>;tag=6083161C-10B1..CSeq: 10 ACK..User-Agent: Sip EXpress router(0.9.7-pre6(x86_64/linux))..Content-Length: 0... . ? 212.190.89.140 -> 212.249.14.236 ................gT.[_...E.....@....c..Y...}9.......fSIP/2.0 486 Busy here..Via: SIP/2.0/UDP 195.129.125.57;branch=z9hG4bK8ec6.3148d226.0..From:417875185 51 <sip:+41787518551@bylltel.com>;tag=568D320F-461F45CB000A78E3-40807960..To: <sip:+41787518551@212.190.89.137>;tag=6083161C-10B1..Date: Fri, 13 Apr 2007 08:56:47 GMT..Call-ID: 5A1CFF5D-461F45CB000A78EE-40807960@212.249.14.236..Server: Cisco-SIPGateway/IOS-12.x..CSeq: 10 INVITE..Allow-Events: telephone-ev ent..Content-Length: 0.... U 212.190.89.137:5060 -> 195.129.125.57:5060 SIP/2.0 486 Busy here..Via: SIP/2.0/UDP 195.129.125.57;branch= z9hG4bK8ec6.3148d226.0..From: 41787518551 <sip:+41787518551@bylltel.com 5CB000A78E3-40807960..To: <sip:+41787518551@212.190.89.137>;tag=6083161C-10B1..Date: Fri, 13 Apr 2007 08:56:47 GMT..Call-ID: 5A1CFF5D-461F45CB000A78EE-40 807960@212.249.14.236..Server: Cisco-SIPGateway/IOS-12.x..CSeq: 10 INVITE..Allow-Events: telephone-event..Content-Length: 0.... ? 212.249.14.236 -> 212.190.89.140 ............|ovW. ..5.izE.....@.@..&..}9..Y.........ACK sip:+41787518551@212.190.89.137 SIP/2.0..Via: SIP/2.0/UDP 195.129.125.57 ;branch=z9hG4bK8ec6.3148d 226.0..From: 41787518551 <sip:+41787518551@bylltel.com>;tag=568D320F-461F45CB000A78E3-40807960..Call-ID: 5A1CFF5D-461F45CB000A78EE-40807960(a)212.249.14.23 6..To: <sip:+41787518551@212.190.89.137>;tag=6083161C-10B1..CSeq: 10 ACK..User-Agent: Sip EXpress router(0.9.7-pre6(x86_64/linux))..Content-Length: 0...