Comment 6 for bug 1516690

Would be interesting what your systems have in common. The most suspicious ones are gtk+ version and window-manager in use.
Do you both use "compiz" and gtk+ 3.10.8 on Ubuntu/14.04?

Reproducing it with another window-manager might suggest it being a problem of plank.

As a note, clicking on the dock should not make it hide in any case. This is only suppose to happen when the mouse cursor leaves the dock.