Audio Systems: No sound from speakers - car audio, fuse box, rear speakers

Question
My 16 yr old daughter has an aftermarket clarion db345 cd/radio (200 watt) in her 95 honda civic.  A few weeks ago, the speakers started losing sound intermittently.  there are only two rear speakers hooked up, and both would lose sound.  at first, problem was intermittent - when she hit a bump, when door slammed, when she started car/radio sometimes it would have sound, sometimes not.  The unit is getting power (settings, clock, etc are working).  Now in the last few days, the speakers do not have sound at all. This is true for both the radio and cd.   Her friend took a look at the unit, all wires were secure going into the unit and at the speakers.  the fuse on back of unit was ok.  Could the unit itself be bad?  I hate to see her have to buy a new unit if it is something else/something minor.  do we need to check the car fusebox?  YOUR HELP IS APPRECIATED!!

Answer
this could be difficult to find.  there may be a speaker wire that goes around a sharp piece of metal of the car and shorts out against it.
Does the cd player stay on and apear to be playing while the sound cuts out?  if so your problem is definatly not in the fuse box. You could try pulling your own wires to the rear speakers. you can just pull them down the middle of the car for a week or two to see if that makes a difference and if it does you've probably found your problem and you can run them more discreetly later.
Good luck and let me know how it goes!