It may be a padding/margin issue or interference between the moduletable code and the box code.
I suggest going into the index.php and removing the xml prolog from the head code. Removing that code puts ie and firfox almost on the same page with each other.
You may then find that both browsers have the same problem in which case you can safely tinker with the css fixing the problem rather than fixing it for firefox and mucking it up for ie.
Sorry, I could give you a driect answer, but if it were me, I would do the above and then tinker for an hour or two.
