I use Firefox v. 11.0 No problems seen like you have. As for the font issue, look at the source and see if it is making a font call for one you don't have and that no viable alternate has been designated. When you use fancy fonts in a web page, it is considered proper to also code and "alternate" - usually just the plain ol' font a browser normally uses. I got so many fonts that rarely do I have a font problem with anything.
Bah, I just looked at it is running an external style sheet, so who knows what font it thinks it is using.
I remembered a plugin I had installed:
font:13px 'Segoe UI',Arial,Verdana,sans-serif; (body)
font-family:Trebuchet MS,Tahoma,Verdana,Arial,sans-serif; (.ui-widget)
Segoe UI is probably the problem. I'd have to look to see which in that list is supposed to replace it if it isn't there. Then again it could be that your browser is just barely old enough that it don't understand some of the CSS markups. The current IE is 9 - it shouldn't be that far behind.
font:13px 'Segoe UI',Arial,Verdana,sans-serif;