You seem to have managed to solve your problem.
Still, if you're referring to a recent bug in Firefox that makes it 'disobey' the system-wide font settings in Ubuntu, this may help you out: http://www.uluga.ubuntuforums.org/showpost.php?p=8193420&postcount=11.
In short, the bug makes Firefox always render website fonts (and its chrome GUI fonts) anti-aliased (AA). The link above demonstrates how you can edit this and make Firefox always render all fonts crisp and pixel-ish, without any AA (this is especially good for webdesigners and people like me who hate anti-aliased fonts because of their visual artifacts).
The fix requires that you have root (a.k.a. admin) privileges (many tutorials on how to 'go root' are available online).
BTW, I'm a total newbie at Linux and Ubuntu is my fist Linux distro, which is why I approach such annoying 'bugs' from an end-user point of view (i.e. quick fixes). Despite this, Ubuntu 10.10 has been a mostly great experience for me and I wholeheartedly recommend it (as well as support all GNU/Linux distros and the open-source and free software movements). :)
I hope this helps. Cheers.