Any app that attempts image or movie conversion locks up Last week I made the mistake of opening an old AVI file, which QuickTime automatically converted to m4v. Well it tried anyway; when it got to the end it locked up.

Since then I cannot do any sort of image or movie conversion. QT Player continues to die immediately after launch. Any other program that tries to convert anything also locks up (beach ball). For instance, I just tried to export an image from iPhoto - dead. 

I assume that there's a file somewhere that lists which files QT was working on, and it keeps trying to open/convert them (I can see the windows open, then die). Does anyone know where this might be?
QuickTime in Mavericks saves it's application state to /Users/USERNAME/Library/Containers/com.apple.QuickTimePlayerX/Data/Library/Saved Application State/com.apple.QuickTimePlayerX.savedState/. If you rename that last folder, then QuickTime should then essentially launch with a blank slate.