I recently upgraded my machine to Windows 8.1 Pro in order to use Hyper-V for Windows Phone development but ran into another issue. I also have Ubuntu set up on virtual box but now can't access it because of the following error:

VT-x/AMD-V hardware acceleration is not available on your system. Certain guests (e.g. OS/2 and QNX) require this feature and will fail to boot without it.

Are there some permissions I have to set for this? If so how?

Thanks,

Mike

The Phone Emulator requires Hyper-V.  The installer enables it silently.

VirtualBox and Hyper-V cannot be running at the same time.  They both require direct access to the virtualization extensions of your processor.