Mine plays them fine. Try playing them on a different CD player and see if they work there . . . otherwise sounds like maybe you burnt them in the wrong format?
Nero-burned CD-R's work fine in my '01 GT, though I sometimes get a little skipping on the last track... think I tried to squeeze a bit too much on one disk.
Well these new ones that I recorded with Nero in music format didn't work either so I don't know what I'm doing wrong. It says 'Bad Disc' on the head unit. The discs aren't bad, they work on my computer and home stereo.