Firefox fonts slightly move with certain actions
In Firefox 18.104.22.168, when I mouse over a link or when the page loads, text will sometimes slightly jump left, right, up or down maybe 2 millimeters. It seems almost completely random but happens quite frequently and is very annoying. I have a lot of font packages installed. This jumping also happens on the text in the Firefox tabs.
Also, I believe a related issue is if I have say an XTerm over Firefox and I close the XTerm, the area where the XTerm was will slightly jump back in to position, about a 1/2 second after the XTerm is closed.
I've been having this problem on multiple distributions: Debian, Slackware, and Archlinux.