Why using Virtualization is making system hangs?

[Bill Stanley]

> Can one precisely tell me why the system hangs so often while using
> any guest in the host Ubuntu? Also, "Ctrl+Backspace" makes the logout
> of the host irrespective of the guest distribution in VM, is it
> normal?

You are very vague about your problem.  Could you state the version 
number of the host. the name of the virtual machine software and its 
version (VirtualBox, VMware, etc.) and also the guest machine OS.  If it 
seems that a particular application is involved, that would be helpful 
as well.

Bill Stanley