No submenus in IE

Dear,

The Nice Menus module is great! However, I have some serious problems with it.

The menu on my website (test.puype.be) works fine in Firefox, however in IE the submenus do not appear at all!!

According to me this has nothing to do with visibility problems mentioned in the Nice Menus FAQ, since the submenu is simply not shown, not even in the menu its block itself.

The module Nice Menus is installed in "/sites/all/modules/nice_menus/", my theme in "/sites/all/themes/".

Nothing special in my page.tpl.php file, relative positioning only used for my three circles at the left (and deleting these positioning tags did not help).

My source files can be fount in "test.puype.be/sources.html"
Anybody any idea?

Thanks in advance! I am becoming quite desperate...