the fans should be even on your computer if you have one on the cpu then you should have one blowing out. if it was over heating it wouldn't freeze it would shut down and give you a series of beeps; also if it was a heating issue it wouldn't even boot up (if its is a newer chip/mb). if just the browser is freezing i would think it has more to do w/ system files or your ISP(cable connection)... i would make sure your browser is up to date as well as your video driver. then clear all temp internet files and cookies...

that should get ya started