Which knoppix version did you take?

Older versions worked fine, while the latest knoppix 5.3 ends in Kernel Panik when trying to mount root fs
Booting in verbose mode shows that the kernel has tried to mount root as raiser, ext, fat, iso,... filesystem. But to get pxe-boot working afaik another kernel is needed. It should be one with ip-kernellevel-autoconfiguration, root-over-nfs and some other spezial kernel-features activated. One can take a brief look on /tftpboot/vmlinuz and /boot/vmlinuz-2.6.24, same filessize... Seems like someone made a mistake when packaging knoppix 5.3 dvd

well, to get it working, i think we have to compile our own nfs-root-capable kernel, at least until 5.3.1, (or use older version)