Well, my flash plugin in Fedora 9 wasn't working. Besides that, I was getting a strange "s" website being looked up for when I started Firefox.
After days of debugging, I just went to: System > Preferences > Personal > Preferred Applications and selected "Firefox" instead of "Custom", which I didn't set in the first place.
After this, Firefox worked fine again! Just wanted to post it so, if you're having the same problem, you know... and I don't forget!