I ran into the same problem after changing my dock assembly to fix a non working mic. GSM 3G/Edge hardly ever comes up but the "o" or 2G shows just about all the time. It's been 3 days like this and I've opened up my phone like 6 times trying to figure it out. I haven't restored my iPhone but from what I been read it doesn't look like it's going to work. Maybe getting another dock assembly might do the trick.. Did you or anyone else resolved this problem?
Answer to: No Service following Dock Asembly Replacement