Hot Corners stopped working at startup

I recently bought Leopard and yesterday enabled and set up my spaces. I set my system prefs under "Expose and Spaces" so that top left would start screen saver, top right would show spaces, bottom right would show desktop. It worked great yesterday, but upon startup today, hot corners aren't responding. I checked my settings, and they're exactly the same as they were yesterday, all correct, but hot corners won't work. Any idea what might be happening?

Thanks.