Also, have you tried looking into Windows' "Event Viewer" to see what might have been occurring at or around the crashes? From an admin-level account: Control Panel > Administrative Tools > Event Viewer > explore the System, Security, and Applications categories. You'll be looking for red-icon errors that might have been registered around the time/date of both crashes (and perhaps even before, but which didn't necessarily cause an outright crash) to see what might have been involved. Often there will be a "smoking-gun" trail that points to some kind of involvement of other things besides what seems to have been running at the time of the crash.
Opera is such that its open files can be corrupted if it's simply open during crashes caused by other sources.