I have been experiencing the same problem you describe and not many people seem aware of it. Looking at dmesg output it shows a message telling "IDE: late registration of driver". Looking for that in Google it points you to kernel.org where it seems to be an issue with kernel 2.4.22. The last Knoppix I have been able to boot flawlessly was 2003-06-06 which is the last one of the recent Knoppix releases to have kernel 2.4.20. From there, all releases have had 2.4.22 and I have been unable to run any of these. If I had give Knoppix my first try today I would have say "Nice, when it works!". Having experience with Knoppix for almost a year, I have resorted to multiple 06-06 homemade customizations, missing some of the fun in current releases, like toram switch.