You have a few errors in your CSS though they probably aren't the problem.
Your code, however, is another story and just testing it gave out 864 errors:
Many are plugin related, but aside from that you need to clean up your code where you can and then take it from there. IE is't good with CSS but then IE7 is coming.
I dunno, clean code will ensure you can clearly label IE at fault, otherwise it looks like your code may be the problem. IE also may require several hacks which can be found by searching these forums for IE Hacks and visiting asite caleld absolute positioning (I think).