Comment 6 for bug 1326688

A quick work around that I've found.

2nd monitor attached to a laptop.

Enable second monitor as primary.

Second monitor appears to the left of the laptop monitor.

Panning problem occurs.

Go into the gnome 'Arrange Combined Displays'.

Reverse the order of the monitors (2nd now arranged to right of laptop monitor).
Apply and Confirm settings.

Go back into 'Arrange Combined Displays'.

Reverse the order of the monitors again so the external display is once again to the left of the internal display.
Apply and Confirm settings.

Panning problem is now fixed.

Not a solution but....