I did start from scratch. I took your original code and made some basic edits (changing width of submenus, adding some gradients, and changing the subitem names). My result was that the submenu would show correctly, but when I attempt to select a subitem, the submenu disappears.
The code you are now giving is indeed my code, but it is not what I'm seeing online, behind the site you linked
. There I see the following code:
with the subMenu not being a child <ul>, but a separate div, not being a child of anything. That is the weirdest menu I've even seen.
However, assuming that you are now talking about a new menu that is not online yet, I tested your latest code, and indeed the filter seems to be the culprit. In IE7 there is no more dropdown, but if I outcomment the filter, everything work fine.