Probably a strange question but do you put stickers on your cds, when I had a multichanger fitted a few years back I was advised against doing so as what you have described happens a lot.
Don't know if you are interested in spending a few quid but this seems to be the best UK site I have found for new hardware, have just ordered a new MP3 player which means very little changing of disks, now how to explain to the wife that I will be spending half my next day off stripping off the dash of me car to fit said new toy...
incarexpress