It is probably related to your PC's HW versus Knoppix (Linux kernel). Me, I'm a Knoppix nut and have tried Knoppix on probably 30 different computers (friends PCs, relatives PC, PCs at work, my PCs) from 8 years old to brand new. I have never had a locked up desktop crash. I have seen one of my own PC (Asrock K7S41GX) do weird things (NIC would not work, 3x slower bootup) when APIC is turned on. I boot it with 'knoppix noapic' and that cleared it right up.
I hope this helps.
James