Computer Freezes - Facebook Application

I play a silly game with co-workers on Facebook called, "FarmVille".

The game has been flowing smoothly until now. If I put the game on full screen, the computer will freeze, but if I press ctrl, alt, del it will close the game off and all is ok.

Then just recently, the game will load, but the computer starts to freeze as soon as I play it. Must be all them points I'm starting to rack up, eh? lol

The CPU usage soars to 100%

XP
FireFox
Computer is almost 5 years old.