Playback of any clip crashes CS 5.5

I have been using adobe premire pro cs 5.5 for months and it has worked flawlessly. Now, when i try to do some edditing today, every time i try to play any clip on the timeline the program crashes, no error message, just the windows message: "adobe premire pro cs 5.5 has stopped working". sometimes the audio of the clip will play for about 2 seconds before the crash but the video never plays. i cannot think of any reason why the program would stop working so randomly. i am using windows 7 64 bit if that helps