Hi, i've come trough a similar problem :
Using Knoppix DVD 4.0, everything was working fine, exept i could not use any USB key.
I found the solution when comparing Knoppix 4.0 DVD with Knoppix 3.9 CD Versions. Using the latter, my USB Mass storage device was automatically detected.
In fact, you'll need to load "ehci_hcd" module (or ehci-hcd, can't remember...)
So just type in a root console, after booting :
If the system can't figure out where ehci_hcd module is, try reaching /lib/module/2.6.X/kernel/usb/misc , or somewhere near that. You'll try to get in the directory containing "ehci_hcd.so", and then
If everything works fine (and you've got the same problem i had), an USB key icon will automatically appear on the desktop... linked to your detected USB device !