I was having the same problem for a long time after I transferred everything from my old laptop to my new one. It was very frustrating, I tried everything I could think of and read about to fix it and nothing worked for me. I was just about to give up when I stumbled upon a solution.
From my Desktop I right-clicked on the XBMC shortcut and selected "Troubleshoot Compatibility". It decided that I should run it in windows XP service pack 2 compatibility. I said "Okay Windows 7,... give it a shot!"
Whammy, it finally fixed my problem for me. I should have just asked Windows 7 earlier.