Plank closes unexpectedly and does not restart after launching a full-screen game from steam

[Nathan Lowe]

It doesn't happen every time, but pretty close to it. It also doesn't happen for every game. After closing the full screen game, Plank (and WingPanel, see https://bugs.launchpad.net/wingpanel/+bug/1380125) is gone. It does not appear to get restarted by Cebere, and you have to reboot to correct this.

If it helps, I should mention that I have a secondary screen attached via HDMI.

===
Elementary OS 0.3 "Freya" Beta 1
Pantheon Desktop (Gala WM)
Intel HD 4000

Plank Debug Log:
[INFO 12:36:59.049880] [AbstractMain:170] Plank version: 0.7.1.1092
[INFO 12:36:59.049938] [AbstractMain:171] Kernel version: 3.13.0-36-generic
[INFO 12:36:59.049975] [AbstractMain:172] GLib version: 2.40.0
[INFO 12:36:59.050013] [AbstractMain:173] GTK+ version: 3.12.2
[INFO 12:36:59.050041] [AbstractMain:175] + HiDPI support enabled
[INFO 12:36:59.050069] [AbstractMain:177] Wnck version: 3.4.9
[INFO 12:36:59.050100] [AbstractMain:178] Cairo version: 1.13.1
[INFO 12:36:59.050133] [AbstractMain:179] Pango version: 1.36.3
[WARN 12:36:59.057421] Couldn't connect to accessibility bus: Failed to connect to socket /tmp/dbus-7H5ChrgutG: Connection refused
[INFO 12:36:59.082791] [WindowControl:62] Window-manager: Mutter(Gala)
[DEBUG 12:36:59.085865] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/settings'
[WARN 12:36:59.095061] [Preferences:184] '/usr/share/plank/themes/Pantheon/dock.theme' is read-only!
[DEBUG 12:36:59.095112] [Preferences:328] Loading preferences from file '/usr/share/plank/themes/Pantheon/dock.theme'
[DEBUG 12:36:59.097050] [ApplicationDockItemProvider:72] Unity: Initalizing LauncherEntry support
[DEBUG 12:36:59.097214] [ItemFactory:155] Loading dock items from '/home/nathan/.config/plank/dock1/launchers'
[DEBUG 12:36:59.097601] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/ubiquity.dockitem'
[WARN 12:36:59.097805] [ItemFactory:171] The launcher 'file:///usr/share/applications/ubiquity-gtkui.desktop' in dock item '/home/nathan/.config/plank/dock1/launchers/ubiquity.dockitem' does not exist
[DEBUG 12:36:59.098123] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/midori.dockitem'
[WARN 12:36:59.098267] [ItemFactory:171] The launcher 'file:///usr/share/applications/midori.desktop' in dock item '/home/nathan/.config/plank/dock1/launchers/midori.dockitem' does not exist
[DEBUG 12:36:59.098553] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/maya-calendar.dockitem'
[DEBUG 12:36:59.099068] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/switchboard.dockitem'
[DEBUG 12:36:59.099459] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/totem.dockitem'
[WARN 12:36:59.099608] [ItemFactory:171] The launcher 'file:///usr/share/applications/totem.desktop' in dock item '/home/nathan/.config/plank/dock1/launchers/totem.dockitem' does not exist
[DEBUG 12:36:59.099878] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/thunderbird.dockitem'
[DEBUG 12:36:59.100332] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/pantheon-files.dockitem'
[DEBUG 12:36:59.100783] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/pantheon-terminal.dockitem'
[DEBUG 12:36:59.101202] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/google-chrome.dockitem'
[DEBUG 12:36:59.101701] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/jetbrains-idea-ce.dockitem'
[DEBUG 12:36:59.102203] [Preferences:328] Loading preferences from file '/home/nathan/.config/plank/dock1/launchers/scratch-text-editor.dockitem'
[DEBUG 12:36:59.127217] [ApplicationDockItemProvider:165] Unity: com.canonical.Unity lost
[DEBUG 12:36:59.133169] [DockWindow:283] dock window loaded
[WARN 12:37:16.792475] Failed to fetch xids: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: No such interface 'org.ayatana.bamf.application' on object at path /org/ayatana/bamf/application/0x17cb360
[WARN 12:37:16.792593] [WindowControl:117] plank_services_windows_window_control_get_num_windows: runtime check failed: (_tmp2_ != NULL)
[WARN 12:37:22.845719] Failed to fetch xids: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: No such interface 'org.ayatana.bamf.application' on object at path /org/ayatana/bamf/application/929449545
[WARN 12:37:22.845831] [WindowControl:117] plank_services_windows_window_control_get_num_windows: runtime check failed: (_tmp2_ != NULL)
[WARN 12:37:33.525527] [Gdk] The program 'plank' received an X Window System error.This probably reflects a bug in the program.The error was 'BadMatch (invalid parameter attributes)'. (Details: serial 6121 error_code 8 request_code 62 (core protocol) minor_code 0) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the GDK_SYNCHRONIZE environment variable to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.)
Trace/breakpoint trap (core dumped)

[M4he (mahe)]

Seems to be related to Intel's video driver and games using the Unity3D engine.
I've got 2 setups: 1) Desktop PC with Nvidia GTX 660 and 2) a MacBook with Intel HD 4000. Both run the exact same setup: Xubuntu 14.04 x64 with Openbox standalone & plank.

System #1 runs any Unity3D game and plank just fine. On system #2 plank crashes with the Gdk error message mentioned in the report above as soon as a Unity3D game is launched (Hexcells Infinite for instance). This happens both with compositing enabled (compton glx) as well as with no compositing at all.