Sounds that you've installed a Firefox version from the Ubuntu software repositories.
Such a version needs to be updated form the Ubuntu software update and can't be updated directly via Help > About Firefox.
You will have to install the official Firefox version from the Mozilla server if you want to update yourself instead of waiting till Ubuntu offers an update.

• http://kb.mozillazine.org/Installing_Firefox#Linux

Thank you for your reply! I didn't install the update, it updated automatically. You'd think it would do it correctly! Anyway, I wnated to put back v13 but it isn't working because I don't know where to extract it to exactly. Guess I'll wait for Ubuntu to have an update.