Firefox History Problem

I just came home from work and went on my Firefox, and I checked for a site I was on yesterday, though when I clicked "Show All History", there was nothing there. So I just figured that it deleted itself, so I went on a few sites and then checked it again and there was still nothing.
I haven't touched any of the settings, they have never been touched. I tried restarting the Mac, but still nothing. Does anyone know what might be the problem?

*Edit*
I can't even do anything now, I can't even delete my browsing history in my address bar. I deleted Firefox and reinstalled it, never worked, so I installed 3.5 Beta 4, and still nothing. I clicked to delete all Private Information, and nothing. I click my history button next to my address bar, it give me my history there though it won't let me delete it. I'm so frustrated.

To get the ball rolling. Are you using a standard user account or the guest account?

Reinstalling usually won't fix this type of problem, which is probably on the user account end of things. I have seen Firefox profiles get fsck'd up from something as small as the user trying to change his/her account name.