Maybe this will make the issue clearer…
chamber.umbrellahost.net
When you roll over Chamber Info (first menu item) and the page is NOT scrolled up, the dropdown menu is nice and wide, when you scroll the page up a bit and roll over the same menu item, the dropdown is very narrow.
I know this is related to the header class “scrolled” but I can’t find where it’s messing up the dropdown menu width.
Hope this helps!