IIRC, the CD-R music cd's have a key on them that non-computer CD-Rs use. Bascially, if you have one of those rare component rack cd-r burners, it *requires* that you use the music CDs or it won't burn. This is because RIAA sued the cd-r makers saying that cd-rs take away their business, so they get money for every "music" cd-r sold. Super LAME.
As far as usinf the "music" type cd-rs in a PC, I think they're supposed to be the same... it just that you paid RIAA to store your data!!
I'd check the usual culprits: fingerpirnts, scratches, bad burns, etc.