If nothing else is helping. As you see it's not a general problem so probably a fresh Windows may help indeed. But I can not promise anything...Should I try a Windows reinstall?
Before installing a fresh windows you could also try to remove all MP1 and MP2 related folders. That helped me once with strange failures in TV3, that nobody could explain.
First uninstall MP2 and then delete the folder C:\ProgramData\Team MediaPortal\