Create a new profile as a test to check if your current profile is causing the problems.

See "Basic Troubleshooting: Make a new profile":

• https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-make-a-new-profile

There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.

If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

See:

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

I restarted with all addons disabled, but no dice. I think the problem may be because I am using the Linux version; I'm on Fedora, but I heard there were problems with the Ubuntu one.

At any rate, I haven't been using this install of Firefox long. I'm also unable to install addons from an external file or from the buttons on the Firefox gallery; I have to have it search from inside the menus, and that didn't help when it turned out to not be able to find Firebug.

Where can I go or who can I ask for help with this?

Hm, restarting made installing addons work. >.>

Aaand there was a software update that fixed it. >.>; Sorry, thanks.