FIOS Video/Audio Dropout

Over the last several weeks, our FIOS HD DVR/Receiver seems to drop both audio and video several times per hour. The TV screen simply goes to black for about 3-5 seconds, then the program resumes.  We’re also seeing problems when programs are recorded: on playback, the video will suddenly freeze, then begin playing for about 2-3 seconds, then freeze again.  This cycle continues until we simply quit and delete the recorded program.  We’ve tried everything, including shutting down the receiver and unplugging it for a few minutes.  Anyone having similar problems — and how can we resolve this?