I have the same problem with an Alps touchpad on my Lat D600. The left buttons just stopped working. Reinstalled my driver: nothing. Tapping works, so I can still use it, though dragging and dropping is a pain. If I switch the right button to "click," the right button stops functioning (it still works normally in default mode). So I figure it is a driver/BIOS problem. I e-mailed Dell (no way in hell I am calling them again after wasting hours of my life on a problem I ended up solving by reading these boards). They sent a tech out to replace my touchpad. Though I doubted this would work, it didn't take any time. I now have a shiny new touchpad installed by an extremely efficient and friendly tech. And I still have the very same problem. If anybody finds a non-hardware answer, my new left button is waiting to be clicked.