can’t choose bottom category

When writing an entry, I can see the menu with categories. And A scrollbar on the side, because the list is long and contain many categories. When I use the mouse on the scrollbar to move it down it looks like http://img303.imageshack.us/img303/529/wpprob17ka.gif *BUT* the very second my cursor is over the categories instead of the scrollbar, the scrollbar go up and make it impossible for me to choose the category at the bottom: http://img303.imageshack.us/img303/5838/wpprob22br.gif – what is wrong? how can I fix it (other than having fewer categories). PS! Please note I use the Danish version 😉