I thought I would drop a line to share my experiences with this problem. I was also having the same problem. On certain programs the drop down menus would open briefly and then disappear. It was a very frustrating little glitch. Anyways, I searched through many forums and didn't really find any solutions. I have an optical mouse. I did solve it though, here is what I did. I am running XP by the way. I went to control panel, then system, clicked the "Hardware" tab, and then clicked on "Device Manager". I went down and clicked on "Mouse and other pointing Devices". What I found when this tab was expanded was that I had two "Logitech HID-compliant Cordless Mice" installed. I right clicked on the lower one and went to "Properties" then to the "Driver" tab and then to "Uninstall" at the bottom. After it was uninstalled everything worked fine. Hope this helps someone!