Strange invisible window causing 'dead zone' in Unity

[flibs69]

I have a very strange problem. Every so often a strange window will appear on the screen - well, I say "appear", but it can't be seen. I know it's there though. It creates a sort of 'dead zone' on the screen - always in the same place.

xwininfo: Window id: 0xe1ce72 (has no name)

Absolute upper-left X: 438
Absolute upper-left Y: 299
Relative upper-left X: 438
Relative upper-left Y: 299
Width: 502
Height: 222
Depth: 0
Visual: 0x21
Visual Class: TrueColor
Border width: 0
Class: InputOnly
Colormap: 0x0 (not installed)
Bit Gravity State: ForgetGravity
Window Gravity State: NorthWestGravity
Backing Store State: NotUseful
Save Under State: no
Map State: IsViewable
Override Redirect State: yes
Corners: +438+299 -426+299 -426-247 +438-247
-geometry 502x222+438+299

I can't identify what process has created it, and I can't get rid of it without logging out (xkill does nothing).

Any ideas for how I can find out what is opening the window? Has anyone else come across this happening?

Ubuntu 11.04

Linux laptop01 2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:24 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

[flibs69]

I am looking at the /usr/lib/unity/unity-panel-service process - I killed it, the process auto-restarted, and the window seems to have vanished. I will try it again next time it appears.

[flibs69]

Ok, I understand this is a known bug, #755459 - https://bugs.launchpad.net/ubuntu/+source/unity/+bug/755459