My copy of Bridge CS6 suddenly stopped showing a preview image for video files and does not play them either. Lightroom 4.4 and Lightroom 5 also do not recognize video files (.mov's, .avi's, m-pegs...). My Lightroom used to have no problem playing them.
Bridge CS4 sees them and plays them as normal.
I purged my video cache in Lightroom, uninstalled and reinstalled it, updated Quicktime and am running OSX 10.8.5.
Here is a link for LR reset http://www.lightroomforums.net/showthread.php?14226-Resetting-%28or-Tr ashing-%29-the-Lightroom-Preferences-file