I have exactly the same problem and I can't even get into Settings - My Nokia (It comes uo with Internal Error Application 'Settings' Closed)to give you the serial number ?
I've tried my wife's sim card on the same contract and exactly the same error message.
Everything else like email over wifi and apps are working fine is purely then sim signal and connection ?
Frommemory is on PR 1.3 and been working fine up until today, it's not clocked and I haven't downloaded anything that might conincide with the fault - any ideas