System: openSUSE 13.2 - KDE 4.14.8 - Xorg 11 601 000

lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 82G965 Integrated Graphics Controller (rev 02)

During normal use, doing things that I do many times each day, I started my IDE (Phpstorm) while running Firefox, Chrome, Thunderbird and Konsole.
A Youtube video was playing in Chrome.

Instead of the first small IDE window, the Plasma Desktop panels disappeared together with all the window decorations (borders menus etc...).
A big greyish window was left behind, with pieces of other windows showing around it.
Any attempt to switch between running applications failed.
Hitting Ctrl-Alt-Backspace twice did reset X11.
Virtual consoles were working, so I used init 3 and then init 5 to restart all the processes.
In both cases, after login, the plasma desktop reappeared, but not the window decorations.
I had to reboot to get the system back to normal.

When I looked at the journal, I saw:
Jun 24 18:47:19 bigboy kernel: [drm] stuck on render ring
Jun 24 18:47:19 bigboy kernel: [drm] GPU HANG: ecode 0:0x9f47f9fd, in chrome [9663], reason: Ring hung, action: reset
Jun 24 18:47:19 bigboy kernel: [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
...
Jun 24 18:47:19 bigboy kernel: [drm:i915_reset] *ERROR* Failed to reset chip: -19

with instructions to report here.