DockbarX appears to lock-up and has rendering problems

Using 0.90.3-2~webupd8~precise on Ubuntu 12.04 with Cinnamon desktop. Running in stand-alone mode.

Within the last few weeks (month?) I've noticed that after running for a while (perhaps a week) something degrades, and when I mouse over an item on Dockbar's dock, no pop-up menu will appear. Likewise for right click. I'll sometimes see a rendering artefact coincident with this that appears like a transparent rectangle extending across my desktop that is sized and positioned to match where a pop-up menu would appear (though at the moment one is appearing on the far right of my screen, some distance from the dock). I can slide windows beneath this transparent box, but the image within the box remains frozen, and attempting to click on anything covered by the box does nothing.

The transparent area does seem to appear in response to an action that should display a pop-up menu. After restarting Dockbar there is no transparent area. Hovering the mouse over a docked item that has a long window list results in the transparent area happening again.

This has happened a couple of times in the past month. Sending an interrupt (ctrl-c in the console) to Dockbar had the effect of fixing the problem the first few times it happened. At the moment, killing and restarting it isn't helping. Dockbar displays, but is unresponsive.

In the process table I see:

~% ps aux | fgrep -i doc
tmetro 6394 59.0 0.7 364868 45228 pts/9 Rs+ 01:40 0:27 /usr/bin/python /usr/bin/dockx
tmetro 6398 0.0 0.0 130896 5108 ? S 01:41 0:00 /usr/lib/dockmanager/dockmanager-daemon

Killing dockmanager-daemon has no effect. Killing dockx works, but as above, the restart doesn't fix it.

Any other related process that should be killed/restarted? Is there a Dbus interface that's hanging or something?

I'm running Dockbar from the console, but don't see anything interesting logged. Just:

DockbarX 0.90
DockbarX init
DockbarX reload
Xlib.protocol.request.QueryExtension

Prior to the initial lock-up I saw:

(Pidgin:7425): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent.
(Pidgin:7425): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent.
** (totem-video-thumbnailer:21797): WARNING **: Could not take screenshot: no last video frame
** (totem-video-thumbnailer:21797): WARNING **: Could not take screenshot: no last video frame
** (totem-video-thumbnailer:21797): WARNING **: Could not take screenshot: no last video frame
** (totem-video-thumbnailer:21797): WARNING **: Could not take screenshot: no last video frame
** (totem-video-thumbnailer:21797): WARNING **: Could not take screenshot: no last video frame
** Message: Error: Could not demultiplex stream.
matroska-demux.c(2103): gst_matroska_demux_handle_seek_event (): /GstPlayBin2:play/GstURIDecodeBin:uridecodebin0/GstDecodeBin2:decodebin20/GstMatroskaDemux:matroskademux0:
Got a seek error
totem-video-thumbnailer couldn't get a picture from 'file:///[...].mkv'
Traceback (most recent call last):
  File "/usr/bin/arista-gtk", line 1342, in on_disc_lost
    self.on_preset_changed(self.presets_view.get_selection())
  File "/usr/bin/arista-gtk", line 1306, in on_preset_changed
    model, iter = selection.get_selected()
AttributeError: 'NoneType' object has no attribute 'get_selected'
(totem:3107): GLib-GObject-CRITICAL **: Read/writable property 'object' on class 'ZeitgeistDpPlugin' has type 'TotemObject' which is not exactly equal to the type 'GObject' of the property on the interface 'PeasActivatable'
Executing: pidgin

It would seem that if I launch Nautilus from Dockbar, it logically is a child of Dockbar, and then anything I launch from Nautilus, like double-clicking on a video to launch Totem, becomes a child as well, and the console from thioe children are being seen mixed in with Dockbar messages.

That likely means the messages above are irrelevant, though I seem to recall that there was a totem issue the last time this happened.

Looks like the version of Dockbar I'm using hasn't changed since November, so the problem must be the result of interaction with something else that changed on my system.