I am having this exact same problem when testing on IE7. I thought it had to do with the flash file in the div below it, but I get the same result on any page I visit that has just a jpeg in the div below. I used MenuWriter on another site built with tables and did not have this problem so I know the problem lies with the interaction with the div.
Site with the problem:
Site without problem:
Both use MenuWriter, but the difference is in how the sites are built. Any thoughts?
I see the problem is not that there is a div underneath the nav div. The dropdown disappears when the mouse leaves the div that the navigation is in. I deleted everything on the page, leaving only the one navigation div and the problem still exists. If I extend the height of the div to a height greater than the height of the dropdowns, they will stay. Confusing...