I think your problem might be really simple silly:
margin: 0px auto;
font: 62.5% "Trebuchet MS", Arial, Helvetica, sans-serif;
I know of a weird IE bug: if there's no space between your background image declarations, then IE sometimes misses stuff.
Specifically, I saw IE not working when someone had this:
background:#fff url(foo.jpg)left center no-repeat;
the lack of the space between ) and "left" was the only problem.
See if it helps to add a space in there. It will be cool if that works.
*edit Ryan totally ninja'd me... lawlz!