I'm having the same problem with a knoppix CD I just burned, after checking the md5 checksum to make sure it was OK. Like the other posters, I find that nodma doesn't do squat, but I have another symptom nobody else has reported yet: I can't get the CD out of the drive until I power down and use a paperclip to eject it! Normally, my CD drive works just fine, TYVM, so I know it's not hardware related. I'd like to get knoppix working, as I'm currently using dual-boot Win98/FC6 and my sister's getting curious about Linux. It'd be nice to let her see how it looks on her computer without installing anything before she makes any major decisions!