Is your virtual machine created as 32 bit ? I run Virtualbox 64 bit on a 64 bit Linux host, and I cannot boot Knoppix on a 32 bit virtual machine, although I specifically choose the 32 bit kernel by wriing "knoppix xkeyboard=dk" when booting. Adding no3d makes no difference. It hangs at "Booting the kernel". On a 64 bit virtual machine I can boot Knoppix 32 bit and 64 bit without problems, even without no3d.