Bug#767173:

[Simon Wydooghe]

I can confirm this bug. The entire image freezes (also the video
playback in VLC which was going on). I can move the mouse around, but
cannot get any interaction. If i try to drag a window for instance,
nothing seems to happen. However... When I take over the computer with
VNC (Vino), the desktop is running perfectly fine! The video is still
playing and the window I tried to drag was actually moved. So it's
just the physical video output which seems to fail? Except for the
moving mouse part apparently.