I have installed VirtualBox 3.1.2 (latest) on my Windows 7 (x64). In the VirtualBox I've installed Windows 7 (x64). I have 4 GB RAM installed. The guest has been assigned a 1536 MB RAM. Sometimes the CPU usage on the host goes 100%.
It happens everytime, in a few minutes, after starting the guest. Then it stops responding. Then I have to "power off the machine" from the menu without doing a proper shutdown. It happens with Windows XP as guest too (even when the RAM amount assigned to it was the same). What is the problem?