Cell phone Stops Functioning?

My Nokia 6102i does not respond to any keystrokes, and the image on the screen does not change.  The problem all started when the cell phone would not ring for incoming calls.  I checked and saw that the ringing tone was turned on.  But, many of the ringing 'tones' files were labelled 'corrupted', though weren't before, and I could not open them.  Then the cell phone stopped responding.  It has been working fine for two months until today when it wouldn't ring for incoming calls.  I also cannot hear the opposite end of the line when I receive calls.  What's wrong with my cell phone?  What's causing this problem?