First of all, great plugin. It is very simple to use and integrate into your theme. However I have been having an issue in IE9. When I hover over the main menu the sub-menu appears as expected but then when I move my mouse to select a sub-menu item the whole sub-menu disappears. This makes it difficult to select any sub-menu items in IE9. I have checked and it works fine in FF and Chrome.
Here is a link displaying the issue: