Userform dropdown doesn't go away
 

Hi,
I have a userform with a combo box near the bottom of it. The combo box is being populated from a hidden worksheet. When the user makes a selection from the dropdown, the list still appears in the background as if the userform was on top of it. How do I get the dropdown to disappear after the user has made a selection? XL2007 and XP.
Thanks.
James