I could not get my whs 2011 to successfully back up my new acer ultra-book. The problem turned out to be that whs 2011 did not know how to work uefi based computers.
The answer is a hot fix from microsoft.
http://support.microsoft.com/kb/2781272
A hotfix is available to add backup support for UEFI-based computers to back up to servers that are running Windows Home Server 2011
Hope this helps someone.