My Win 7 box is down at the office, so I don't have a means of testing this at the moment, but I don't think I had a problem with that.
What exact version of FireFox are you running?
Have you tested any other browsers, or other FF versions?
I have a thought that is any easy test -
Save your FF bookmarks, uninstall FF, clean out any folders, do a registry cleaning, reboot, and install a new, clean no plugi-ns version of FF.
I say this because FF is known for having weird cache and plug-in errors.
IE 'renders' weird, FF 'acts' weird -- No wonder people love Chrome (which has its own set of issues) and lets not EVEN talk about Opera -- The ET browser (hehehehe)