Maximum PC

I have an hp dv7 computer running windows 7 64bit.
Just recently after installing mozilla firefox my computer all of the sudden freezes after I minimize/exit from world of warcraft and then shortly after try to open my browser. I uninstalled mozilla and downloaded chrome but the problem continues. I'm thinking it must have something to do with the ram but I'm not sure. I've run memory diagnostic and no problems were detected. I have 6GB of memory currently. Any help/insight to this problem would be greatly appreciated.

ps a week or two before problems started happening I was going to open my laptop to clean the fan but only got to unscrewing and never actually opened it up. I had to turn the computer over idk if that disloged the ram or not but i think it would have shown up in the daignostic.

Thanks for the help!

Just for future reference. I was loading my game and the updater noticed that my video card driver was out of date. After installing the update the problem went away!