Right now the only thing I can think of is that something like the NoScript extension is installed, which is blocking the javascript for the buttons/dropdown etc.
However, that would appear unlikely since I get the impression this is a new install.
So next is knowing which dropdown menus do not work 'correctly' also need a better defined
currently implies that there is some function, but 'wrong'
It could be that your site with the dropdown are using flash or siverlight, although I would have thought you would be prompted about that.
