Dropdown submenu stays visible issue in IE7

Dears,
Could you please help me with following issue I have when browsing my site with Internet EXPLORER 7 ?
I'm searching around but can't find the solution :(

I have a horizontal menubar and when you go with the mouse over one of those menu's there is a SUBMENU appearing in dropdown with the navigation and submenu navigation module.
Sometimes these dropdown menu's keep hanging, meaning they stay visible untill you click on a submenu. (in IE7)
For example: when you go down with your mouse over the submenu's untill you are out of the (dropdown) submenu, so on the BODY-ARTICLES then the submenu is still hanging there... while it should dissapear already.
In Firefox this is working perfectly and in IE7 not.

Can anyone help me with this please , it would be a great help !!

thanks a lot & regards,