Brian,
BTW, the menu works in IE 6 with the default vista theme. The only edit you need to make to bust it in IE 6 is to change the width in edit theme/box/main/item/dimension/width from 160px to auto
I guess a horrible workaround could be to make 2 separate instances of this menu and use the ie6 css style generated from the default theme as the conditional and use the auto width css for everything other than IE6. Sounds like a hassle.
-paul