It used to work/Now it doesn't

[Rob]

Greetings all,

For some reason my CD player will no longer work in Ubuntu 8.10.  I
inserted a known workable DVD (it is a combo drive) just now -- known,
because I have watched it on this same drive -- and it works fine.
However, an audio CD, on which I have previously successfully listened
to 3 tracks will not produce any sound.  

Does anyone have any ideas as to what this could be?  (Audio works fine
for other applications -- listening to radio, for instance.) BTW, I am
running GNOME.  I alternate between GNOME and KDE desktops (and although
KDE always tells me the sound is "broken" when I boot into it, it works
fine -- except for the CD player, of course.)

Thanks in advance for any assistance.

Best Regards,
Rob Fleetwood
Rockville, MD