The css margin settings in #nav li ul ul { margin: -1.3em 0 0 14em;} have no effect in Firefox and I.E.6 for positioning sub-submenus on the primary links menu. Nor does styling #nav li li ul.

Instead, change it to:
#nav ul.menu ul ul
(this is different from my temporary solution in the main project page's discussion)

Hope this will work for all browsers. Could only test the two above.

By the way, am using No Koala! on a 5.1 site with no problems.