This just happened ...
What i was doing at the time:
My default Dual Lister was open with the Find Panel
My custom Find Lister was open and was going through 38 movies getting their duration
It had not finished updating the duration of all the movies when I clicked on a movie with a .mp4 extension and Whammo 
I think it must be pain in the arse Stu Wednesday, sorry for all the grief Leo.
stu.
You probably have a video codec which is crashing when Opus asks it to inspect one of your video files.
See Crash, exit or high CPU usage when viewing certain directories in the FAQs.
Hi Leo,
You were spot on. It appears that the culprit is the Movie Viewer Plugin (the one with the icon that could be quicktime in apperance)
After replicating the crash 6 times with it on and 0 times with it off, I'm going to go with that idea so I can sleep easy knowing it wasn't me screwing around with something for once.
Thanks again Leo,
Stu.