I can 'see' a call coming in on the display, but cannot answer.

[JAHW]

Has anyone had this problem? I can 'see' the call coming in on the display, but cannot answer it. Sometimes it happens when I am mid-text....other times it rings and I can't answer it. When it happens, I lose all sound on the phone. Can't hear music, ring tones.... pulling the battery is the only thing that seems to work to reset it......