BUG: Menu and right drop out menus disappearing when above headline of page

I don't know since when this bug exists, and I'm not sure it happens with all browsers, it is problematic with Firefox 4 (on Windows 7).

The problem is that the page menu dropdown subentries that open up to the right are folding up, as soon as you move onto them, if there is a headline link below.

see example here (using Firefox 4):
http://openmtbmap.org/de/
1.Move mouse over Tutorials, go down to "Karten in Mapsource installieren" wait for the menu popup to the right to show and move your mouse over it. That's working.

2. Move your mouse away so the menu closes.

3. Try to get the menu popping up again - it won't work until you click on the page (no link, just somewhere). Now the menu opens up again, but you will be unable to click onto any menu links popping up to the right under the Tutorials header.


Hope someone can reproduce this bug. The description above is for Firefox4. It is really annoying that the submenus opening up to the right are really difficult to click. Damn, this bug is so bad, that I consider not using subpages anymore.
I noticed on my statistics, that these pages virtually get no traffic at all - because people are actually not able to open them up.

This problem did not exist in old Atahualpa versions with Firefox 3. Not sure whether this is a Firefox bug or Atahualpa bug, but I have 80% Firefox users, so this bug is a really big problem for me.
Chrome seems to cope mostly fine, just sometimes the menu structure breaks down, but it is solvable by clicking onto the page somewhere, and then the menu works fine again. Internet Explorer 9 seems to work mostly fine, but also sometimes the menu becomes bogus.
Overall the delay for closing really is too quick and should be 2-3 times slower - as it sometimes is hard to click onto the titles.