Dropdown Menus Don't Always Work

Firefox 5, suse linux Dropdown menus are often unusable. They show up (display) but when I move the mouse to select a choice from the menu the menu disappears before I can make a selection. This happens with dd menus from the toolbars or on dd menus on various websites. If I close firefox and restart the menu selections from a dd work for a while but then stop working. I have not been able to detect when the dd menus go from working to not working. Anyone else see this? Anyone have a solution? Kind of annoying to keep restarting firefox to get to us dd menus. Tom Kosvic