Fuck Firefox. There, I said it.
When you load the browser (Start the application) what page is your homepage ? there is prolly a bad script on there that's messing with the browser.
Gimme the URL and I'll check it out . Or, go to Start -> Run "www.cnn.com" or whatever page is NOT your homepage. This will start your browser on another page besides the homepage, which is good for troubleshooting.
From there, look into your Java settings (Get the latest versions of everything) and try to browse up to microsoft updates.
Firefox is Netscape and even if you're into PC Politics, Nutscrape is just as evil and indignant as Microsoft.