[Serusers] SER and D-LINK DVG-1120

Hi! Now I have another little problem. I am running SER together with Cisco IP phones and a Allied Telesyn as PSTN gateway. I also have a Cisco router as gateway to some ISDN lines. Today I hooked the D-LINK DVG-1120 box up. Everything works fine and I can make VOIP calls to/from the DVG-1120. But I cant do calls that goes to PSTN gateways. Only receive. A part of the debug messages sais: 11(5344) receive_msg: cleaning up 16(5353) SIP Reply (status): 16(5353) version: <SIP/2.0> 16(5353) status: <400> 16(5353) reason: <Syntax Error> 16(5353) parse_headers: flags=1 16(5353) get_hdr_field: cseq <CSeq>: <1> <ACK> Anyone have any ideas on how I can trace this problem down? Since the Cisco phones (and also the X-TEN softphone) works just fine, I guess my configuration should be fine. Regards, Chris