Simplemenu enabled prevents selecting parent of new term on taxonomy vocabulary

test case:
enable simplemenu

try to add a term on a vocabulary (taxonomy module)
click on the parents box (it does not let you select a parent)
the first term (usually root) is highlighted by not selected
you can select a parent using the mouse arrows up and down

disabling simplemenu will let parents be selectable

this happens on at least garland and golden day themes
on mozilla firefox 2.0.0.1 on winxp sp2