I'm having a similar problem where the N 70 doesn't log on to the network at all. It doesnt matter whether I manually search for the available networks or the phone is in GSM or 3G mode but I can't make/receive calls or send/receive text messages.
Also, even though I have call diversion switched off I see the arrow icon in the top right corner and I know there is some problem, but I can't figure out how to turn that off...
I have tried *#7370# and formatted the phone completely but it hasn't helped.
Could it be a virus problem? Anything else I can try?