Maybe, that is the cause: http://support.micro...b/2850674/en-us? Interesting. So some unlucky people might have their computer rendered unbootable by no fault of their own, and there is no fix? (except, of course, a backup image on a whole separate hard drive, which everyone has) Were there patched theme files in play here? If Microsoft updates components that touch any patched files, it may only be able to load digitally signed files (themes) and thus DWM will fail to properly initialize without theme data. It occurred with a windows update that happened a while back, I imagine it could theoretically happen again...