Hello
I have this problem, while on the internet or just msn, noted as one tries to stop the internet service because it is ringing but this is not displayed, then I introduced the missed call message, and tested and so, give tone to the call and the call simply do not enter.
I and restarted, as shown and believe me is not the solution and as I have read is not good to do all the time, I flashed completely left as the factory and still gives me that problem.

Sorry for my English .