OK, one more message, but I don't have time for more.
If you test the menu on http://www.website-laten-maken-amste...nu_vert_2.html
you will see that it is cross-browser, even with huge gaps between the sub menu items. Then, if you compare my source code with yours, you will see some significant differences. You are not using relative-absolute positioning, for example.
Just rewrite your code from scratch according to my tut, and your menu will be cross-browser, too. It shouldn't take you more than half an hour. Good luck.