I use an Ubuntu Karmic desktop environment for my host. I use VirtualBox with Debian Lenny for virtual machines. Most of the time virtual machines work fine with multiple processors enabled in VirtualBox, but Debian Lenny does have some instability forcing the VirtualBox configuration to use 1 processor to maintain stability. Maybe changing the kernel, particularly to an SMP kernel, is required; this would make sense. I can try that or just leave it as a single core virtual machine which is stable. I’m not really inclined to do anything because everything works fine as is.