THought it could have been water damage to the '3G, but it works fine most of the time. I turn tethering off, disable 3G, switch to airplane mode, give it 5-10min, switch it all back on and 2/3 times it works. Vodem is a different story, but very similar.
Had it bigtime the other night, lost data/sms/voice all in one go. Tried to make a call and it just would not connect out at all, full signal bars, but nothing.