Today I came across a blue screen in VirtualBox 3.0.2 in host Ubuntu and guest windows xp. The problem was related with a file
intelppm.sys. The solution was simple:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Intelppm
And changing the 'Start' value to '4'.
Check this post
here and you will get more info. The post talks about Virtual PC but the solution is the same for VirtualBox