Same problem, but solved
I have a same problem for a while. It is exclusively Firefox problem, and it's not happening in Internet Explorer. It's really annoying (Vista).
The solution that worked for me is just to remove the maleMenu() call from neumalen() function. Basically, neumalen() function now has no meaning (and as I see it, it was only for onresize).
Please, check this in more detail and patch the code accordingly.