I'm running into the same problem. The site is http://www.totalskinandbodyspa.com/preview/
The menu is set in the CSS Menu Writer: Edit Menu Theme as:
top level 120 px wide
1st level 160 px wide
3rd level 180 px wide
As you can see, when you hover over the menu, the drop down shrinks to smaller than what I have it set to and nothing I have done seems to work.
Any advice is appreciated.