You don't want any compatibility settings to be turned on for the Opus executable. We recommend turning off any that Windows decided to turn on.
What kind of file was it? My guess is a component involved in viewing, thumbnailing or extracting metadata/columns from that type of file is probably involved in the crash.
Were any crash logs created that time?
Do you still have all the shell extensions that were disabled before disabled now? If they were re-enabled after things started to work again, one of them is probably the cause.