Videos not playing on computer?

I was watching a video on Youtube a few minutes ago with my little sister when she leaned on the keyboard hitting several buttons. The video stopped and went completely blank (black screen). After several attempts to get the video to play (reloading, trying another video, restarting browser, etc.) I looked at the page source to see if their was any problem there. I didn't see anything unusual (but then I don't know too much about the particulars of internet videos). Then I tried watch the video on a different web browser (First Firefox, then Camino) and neither worked. I right-clicked on where the movie should be and it said "Movie not loaded..." and "About Adobe Flash" which I clicked on. I do have the current version of Adobe flash. Anyone know what might have happened and how I can fix it? I have a Mac OS X Version 10.5.8