I have the same problem. I have two hard drives in hde and hdg. My CD (tried with two different LiteON DVD burners) is in /dev/hda. 'failsafe' works, as does 'knoppix nodma', but 'knoppix26 nodma' does not. I also tried 'knoppix expert' and didn't select any SCSI drivers, but it didn't work.

I had the same problem with Slax, but the newest version fixed that. My guess is that this is related to having the CD-ROM at an unusual location (/dev/hda).