Browser Problem on Reinstalled Vista

Hey guys, I need some help.

I recently got my Windows Vista reinstalled and a memory stick removed to fix a BSOD problem, but now I have another minor problem.
A few times a day, firefox (and IE and Opera) will stop working, simply saying "stopped" when I try to go to a website. My internet connection is still on though, as I can still play Counter Strike. Also, when I try to end the process in task manager, I go to "End Process" but nothing happens, it just stays there. I highly doubt this problem has to do with malware/spyware problems, as it was just reinstalled the other day, it runs great when this problem doesn't occur, and I have plenty of protection. Any1 have any ideas or solutions?

I forgot to mention that the only way I fix this is to restart the computer. Then it works fine again.