Menu: Sub items unclickable in FF

Hello
I’m using the default menu and it works fine in IE and Chrome, and the sub menu items show up and is working. But in Firefox is not possible to click on them, they disappear as soon as I try. (Sometimes I’m lucky and able to hit the sub items before they disappears)

I’m personal always using FF, just tested in Chrome and IE if this error also showed up there, but it doesn’t.

I have very few plugins installed and I have tried to have the all deactivated and no change.

throow.cafedanmark.com