I use GV + SipSorcery + Sipgate without any problems. What I suggest is setting up a softphone (Linphone) and putting in your sipsorcery credentials. Then test to see if that works properly. If it doesn't and you have the same issue, then you know the N900 is not the problem. If it does work, then you may need to look at the advanced settings on your SIP account that you should have added to the N900. You may need to look up a STUN server.

Here is all the info you should need:

http://docs.google.com/Doc?docid=0Ae...M4ZjNjeA&hl=en


good luck