Comment 4 for bug 799202

I believe I found the cause of this regression. The wacom tablet sometimes sends button presses on one of the X devices that does not emit (or has not emitted yet) traditional X and Y coordinates. This confuses the server due to masked valuators and coordinate transformation. The fix is to not generate and propagate any coordinate changes if the incoming event does not have any coordinate changes.

Please test out the xserver-xorg-core package in ppa:utouch-team/unstable after it has built. The package version should be 1.10.2-1ubuntu1.2~utouch1.

Thanks!