audio problem w/ cd-rom and cd-rw

Hi all,
I have a curious problem. I have a new cd-rewriter and an old cd-rom drive. I can listen to audio cd-s only through the headhpone output of the cd-rom because through all other channels - i.e. the headphone output of the cd-writer and through the sound card (independent of which drive it is connected to) - only the right channel works. I have tried several headphones and a new audio cable, too, but it did not resolve the problem. I would highly appreciate any idea why it is so...