VirtualBox can't operate in VMX root mode

If you get this message from VirtualBox:

VirtualBox can't operate in VMX root mode. Please disable the KVM kernel extension, recompile your

type:

sudo modprobe -r kvm_intel

Run VirtualBox again that should fix the problem.

Transparent VirtualBox window with compiz manager

If you getting a transparent VirtualBox window, you can start VBox like this to fix the problem:

env XLIB_SKIP_ARGB_VISUALS=1 VirtualBox

references:
https://bugs.launchpad.net/ubuntu/+source/virtualbox-ose/+bug/292588
http://ubuntuforums.org/showthread.php?t=1160178