I just realised that the root post's problem looks like the issue caused by a recent update to O&O Defrag:
[Directory Opus 9.1.1.8.3352 Crash)
Edit: I just realised I'd already linked to that thread. Can people seeing the crash that W0lfdale reports say if they are using O&O as well? Then we know if there's a connection or if it's a separate issue.