Hi guys, appologies if this has been discussed before, ive tried many searches but the keywords are so generic I get thousands of irrelevant results.

I have a iphone 3G OS 4.2.1 baseband 06.15.00 (ipad, upgraded using redsn0w for the ultrasn0w unlock)

The issue im having is that when I switch on the 3G network, the normal phone signal
(o2) dies, and i get "no signal"
This has started happening since the baseband update (i believe, i hardly ever use 3G)

Does anyone know anything about this? is it somehow related to the GPS not working problem?

Ive tried reseting the network settings to default but no joy, id much appreciate your help.
Cheers
Tom