So far it looks like I can prevent the problem by killing the Touchpad:     xinput set-prop "AlpsPS/2 ALPS DualPoint TouchPad" "Device Enabled" 0     xinput set-prop "PS/2 ALPS DualPoint TouchPad" "Device Enabled" 0 Which one I use depends on whether the laptop is docked or not. The mouse stays oriented 100% after that. I believe the root cause is that the Synaptics driver does not manage the Alps touchpad on the Dell Latitude E6500.
My laptop gets into a state where, when I click on the mouse buttons, it thinks that it's pointing somewhere that it's not. When I click on the mouse buttons, usually nothing happens, although sometimes the right button causes a menu to pop up somewhere else on the screens. I have to go find the window where I was working before, click on the right mouse button to pull up a menu, then go to where I want to work, click on the right mouse button to pull up a menu, and then I can work on that window. Also, selecting with the right mouse button is not implicitly copying, and the middle mouse button does not paste. I have no idea what's causing this. It happens pretty frequently when I work in dual-monitor mode. Things work fine when I log in, then this problem kicks in after awhile. I can clear it by rebooting. I've seen it happen with single-monitor mode as well, just not as often. I haven't seen any posts by anyone else having this problem. I'm running Ubuntu 10.04.1 LTS ("lucid") on a Dell Latitude E6500, with BIOS A23.
Disoriented mouse with dual-monitor