why does this happen

hey uh, why is it that sometimes if I click the back button or try editing a post or do something else on this forum my comp freezes? And it only freezes when I'm on this forum/site, sometimes. My comp isn't a peice of crap but someone'll prolly say it anyway. Felt like asking this since its happened more than 3 times now and now I'm kind of scared to come on this forum for my comps sake..

so if anyone's nice enough to help me out here :confused:

specs please? Also it might be a infection of spyware or virus which will be the cause...maybe.