css menu hover "hangs" in chrome & safari

Greetings - Struggeling with a three-level css menu.

Works fine in FireFox and Opera for mac, but in Chrome and Safari the third level "sticks" or "hangs" as a watermark after you move the cursor away.

I have tried a few different things without lu开发者_运维百科ck.

Live demo here:

http://www.it-stud.hiof.no/~benteh/tmp/

I have cut away everything else, so this is just the menu css & html.

(PS. there are only three levels on archeology, hominins and environmental)

You may be interested to know that removing the "visibilty: hidden" rule from the ".menu ul li ul" selector (on line 105 of the CSS) fixes the problem for me in Chrome. Checked in FF3.6 and it works too - didn't check it in anything else.