Comment 138 for bug 868400

the problem also shows in precise. My touchpad suddenly stopped when i (may) accidentally make a gesture which disable my touchpad (not for the click function). When i did, it displays an osd box(looks like a notification) and then my touchpad is disabled.

when i run dconf-tools and looks for /desktop/gnome/peripherals/touchpad/touchpad_enabled the value is "true".
Then i re-enable it by setting it to false, then true. and my touchpad went normal again.
i think it's because disable touchpad while type feature's bug.