These drop down menus were developed long before ubb 6 contained drop down menus... which is part of the problem. I have no problem with these menus and IE 5.5 or NS4, but they do not work at all in NS 6. What OS are you running on and what is your connection speed?
We are working on another solution presently, but to have true cross-browser compatible dhtml menus will involve some additional downloading until the files are cached in your browser. Bugs are being worked out now, we'll be ready by the time v6 is outta beta... if not sooner.