Thanks for this, couldn't figure out what I was doing wrong with the 3g sip. I have found that so far using the Sipdroid was a pain because I allways had to manually enter the phone number into Sipdroid. Then I found on the Sipdroid website how to change the prefix on the fly. Automatically having the prefix added (I use a 001 prefix) while using Sipdroid had made my day.
FAQ - sipdroid - Frequently Asked Questions - Project Hosting on Google Code The call quality is awesome too!