After having a terrific 2 years with my Bold 9700 I had a free upgrade to the 9780 and I hate it! The little clock whirrs around all the time and freezes the phone and worse, the battery runs down overnight - have tried a brand new battery and it still runs down so there is clearly a fault on the phone. I think that Black Berry have lost the plot - if you want to get tech helo you have to give your credit card number and pay £££££ for someone who doesn't give very good advice. Most disappointed !! Am going to to see an o2 'guru' to see if the phone can be fixed. Meanwhile my old Bold has decided not to work - it doesn't pick up the network signal anymore desoite the SIM being the same as in the new handset. Blackberries - I hate them!!!!
If replacing the sim doesnt work i would try a security wipe, upload the newest OS and see if that helps.... But as Phil_UK said this all seems to be a sim card problem.