Why oh Why IE7 Part 2

Now what gives?

Drop down menus appear fine when you hover the mouse over the top level of the menu.

But when you try to mouse over the rest of the menu (provided you get over some invisible gap that makes IE think you’ve moused off the menu), this happens

Naturally it only happens in IE7. Perfectly fine in Firefox, Opera and Google Chrome. Blargh and blargh again.