[7.075] Firefox/Leopard: Webadmin dropdown-menues don't drop down [NOTOURBUG]

Hi there

On Mac OS X 10.5 [Leopard] with Firefox 2.0 [Mozilla/5.0 (Macintosh; U; Intel Mac OS X; de; rv:1.8.1.9) Gecko/20071025 Firefox/2.0.0.9] the dropdown menues don't drop down [:)] 
but "navigation" with the cursor-keys (up / down) works

On Mac OS X 10.4.xx with Firefox that problem does not appear.

regards

tobi