Does this only happen when you are playing CDs?

I have a 98 Nissan Maxima SE with the Bose sound system in it.
Recently, I've been having problems.  At first, it would be playing
sound through all speakers and after I'd go over a bump, it would for
some reason just play through one speaker.  I would then just move the
volume knob a little bit and it would start playing through all of the
speakers again.

Now, however, it ONLY plays through one speaker (the lower speaker on
the driver's door).  If I put my ear right up to the lower speaker on
the passenger door, I can hear a little bass but not much.  I have
recently noticed that when I turn on my headlights, the display does
not dim and the lights behind the buttons do not come on.  Also, the
balance and fade knobs have no control anymore of where the sound
comes out of - only that one speaker.  I took out the system and made
sure all of the wires were in securely and nothing was frayed, and it
all looked ok.  Any ideas?

Check to see if you are getting power tot he amps in the other speakers.
 The probablity of having multiple speakers fail at the same time is
slim at best.  It is probably the head unit or a relay.  Check the fuses
that run the head unit and the fuse for the bose amps too

The Bose system has a relay that turns on all the amps for each speaker.
In the front passenger seat, it's behind the the panel by the
passenger's right foot. If you listen carefully when you power on your
Bose, you'll hear a click in that direction. That's the relay. Because
you can hear faint sound from the otherwise non-functional speakers,
that tells me your trouble lies with the amplifiers. Your head unit is
probably OK. I would check that relay and go from there to the amplifiers.

HTH

CD