I posted about this in a thread here where I was getting horrizonal and menu bugs. XMBC has issues with the latest intel igpu drivers. This is known and recognized by intel and they said it should be fixed by the next driver update. The solution for gen 3 CPUs is to roll back the driver. For gen 4 haswell, you have nothing to roll back to, but can use the win8 beta driver. IME, however, this trades problems. it fixes the graphics glitch, but breaks my HD audio via HDMI (video still works, but HD audio is listed as unplugged in the setup dialog).