Ok, thanks for the info. May need to give this a bit more testing, but making the following code change appears to resolve the issue:
In styles.css, in #access ul ul
Remove "top: 18px;" (line 427)
(Appears to work in Chrome latest, Firefox latest, and IE 7+)
It looks like having two lines of menu items with that particular theme is causing weird side effects by pushing the menus down further than where they should be. Getting rid of that line should resolve the issue by letting the browser's default positioning take control of the menu's placement.
Dunno what the effect of removing that CSS rule and scaling the menu back to one line would be. If doing both actions causes regression, adding the CSS line back in might fix the issue again.
I hope this helps!