mine occassionaly goes like that, normally around times when tom's is having a problem, or I am d'ling a lot of other stuff. But normally a refresh and it goes away. Are you downloading using xfire or similar?
I'm using Firefox to Tom's since Explorer have some sort of cookies problem when it comes to this website and won't let my log in. I'm using XP Home Edition and use Firefox 2.0 just for toms and explorer for everything else.
I'm using FF2.0 and it looks fine to me. Try clearing your cache and also, try disabling all FF extensions and themes. If this works, enable extensions one by one until you find the culprit.
Although FF checks for extension compatability, there are still some issues. I had a problem with an extension deleting all my tabs everytime I clciked the home button. Turned out that even though FF updated one of the extensions, it left behind some residual crap that messed it up.