This happens both in IE6-8 and FF.

I have a vertical mbmenu like the one in your demo, containing the items: menu1 and menu2. All submenus are ajax-driven (menu11, menu12, menu111, menu112 etc). This bug occurs when I hover over one of the ajax-driven submenus.

Depending on how I hover over menus, sometimes they disappear, other times the subsubmenus are displayed. For example, I first hover over menu1, after a little pause, menu11 and menu12 are shown. Then I move cursor to menu11:

• If I move the mouse slowly, and keep moving it for a little while, the subsubmenu (menu111, menu112) is displayed as expected.
• If I move the mouse fast, and stop right when the cursor is on top of the menu item (perhaps only triggering a single hover event), the menu (menu11, menu12) will stay for half a second, then disappear.

I think that maybe what happens is that the mouseout event from menu1 is triggered after the mouseover event from menu11. Just an idea.

This is pretty annoying, since it means you cannot move the mouse too fast when using the menu. Slow users will never notice it though.

This is the only bug that's holding me back from using mbmenu in a production environment.