kvm vs kqemu
After I updated my Ubuntu distribution to 8.04, I discovered that the virtualization software I used to compile MatlabBGL didn't work with a 64-bit version of Windows XP anymore. No one seems to mention this next fact, but I simply couldn't get qemu/kqemu to work with Ubuntu 8.04 and XP64 with a network interface enabled. Instead, kvm --- the "new" and "official" kernel virtualization module --- worked instantly, it even uses the old qemu/kqemu images.
So don't bother with kqemu under Ubuntu 8.04 --- just use kvm.