Preview: Fullscreen movie turns black after 5s When I open a movie in preview (tested with .mov and .wmv), and I go to full screen, the movie turns black after five seconds, unless I keep moving the mouse. The movie plays just fine in windowed mode, and the issue occurs both on external and internal monitor, and with Caffeine turned on or off. 

I assume there's a timeout setting somewhere. How can I modify this so that I can watch an entire movie in preview?
It turns out this is a known bug with Pathfinder that doesn't interact well (yet) with Quick Look. As a workaround, you can use Quick Look from Finder.