Windows Vista C++ error on startup

I recently updated iTunes and quicktime using the Apple update manager, but when I switched off my laptop and restarted again i got a message which said there was a microsoft visual c++ runtime library error and wouldn't let me boot up. I had to start windows in safe mode and system restore back to before the update. Is this a compatability issue? i have a feeling it's quicktime that's at fault, but obviously I need qt to be able to use itunes