Internal Error. Application 'Phone' Closed.

Whenever I try to call someone or if I pick up a receiving call, the phone closes and I get the error message.

I'm running PR 1.3 (updated last week), but this issue came up a few days ago when I went to a Bell store and tried using a Bell (dummy) sim card. I forgot that the last time I tried it, it didn't work, but no error came up. I don't think that would have done anything.
I switched back to my Rogers sim card after.

I know that it's not my sim card or the network. I tried a different Rogers sim card and I can only send & receive text messages. I even tried using a Mobilicity sim card (but can only send & receive text messages).

Last night I flashed it and installed with PR 1.3, but no luck again.

I'm thinking of calling Nokia to send it off for repair, but I don't want to send it off if it's a simple fix.