You might get the following error when starting AVR Studio.
"Only some of the Microsoft Visual Studio 2010 products on this computer has been upgraded to Service Pack 1. None will work correctly.... Install SP1 from following location (VS10sp1-KB983509.exe)... AVR Studio will close now."

To fix this, download the Visual studio sp1 web installer or the standalone installer and run repair, and it seems to fix the problem. The link is