Not sure if they are responsible, but you have a lot of errors in your UBOnline.css stylesheet, and a few in the MTStyles.css stylesheet. I would recommend going over to the W3's
CSS validator and plugging those two files in, and fixing the errors there.
A couple notes on the errors... "13/18px" isn't a valid entry for font size. "align" is not valid for CSS (it's an old deprecated attribute for various HTML tags). What you want is text-align. I've also recently found that even though the CSS2 rules on W3's own site don't say that a 0 value for line-height is invalid, their validator doesn't like it. Stick a % on that and it's good, or you can ignore it (but it'll make the validator shut up and be more accurate in finding other things.

). Also, there's no such thing as "inline-block" as a value for display. If you want it to be a block element and it's normally an inline element, then you want "display: block;". If you want it to be inline and it's normally block, you want "display: inline;". If you want it to be whatever it normally is, you don't need to specify that property at all.
That should about cover it. You have a stray } in your MTStyles file as well. No idea if any of that would throw IE off or not, but cleaning everything up will make it easier to troubleshoot even if none of that's the problem. One less thing to worry about.