So basically, every profile works except mine, which is the root administrator profile.
Screenshot of my profile:
http://i.imgur.com/WzAbi.png
Someone else's profile:
http://i.imgur.com/pl7u3.png
I've disabled the visitor messaging for myself, as I thought it caused the problem, but the funny thing is that it has nothing to do with it, lol.
I've inspected it with Firebug as well, and the part with tabs is missing, even though it's there for other profiles, LOL!
Thanks!