I have a similar problem with booting from USB-CDROMS.
Hardware are Dell X300 / Toshiba R100 both Laptops with no internal CDROM.
I can boot fine with older KNOPPIX Versions and the 2.4 Kernel and every USB-CDROM/Burner.
But every 2.6 Kernel ends with with:

Cant find KNOPPIX filesystem, sorry.

If there are no methods to boot without ub support. Is it possible to remaster KNOPPIX with a recompiled Kernel without ub support?

Thanks