shifting background in IE

Hi all

I'm having a bit of a problem with a site i'm making:

http://statik.be/misc/reli/menu.php?index=detail

As one can see in MSIE, the background at the top shifts to the left,
while it doesn't do that in FireFox, Opera or Safari. It works fine on
other pages with the same background as well, only this page is
affected. This isn't the first time I come across this problem, but I
can't seem to solve it this time. Usually, I can fix it by making the
content block a little smaller, but not this time. Can anyone give me
a hint on how to solve this or point me in the right direction?
Thanks a lot in advance!

DK