Please describe the problem:
On a Ubuntu Breezy box, the gnome-panel 2.11.90 likes to play hide-and-seek.

It's really difficult because there's no way to reproduce this.

In fact, sometimes, if you change workspace, the upside panel disappear and is
only accessible from the first desktop.  When logged in, all works perfectly
and, at one point, you realize that the up-panel is only accessible by the first
workspace.

well, it's not so easy : sometimes the panel will reappear !  Yes ! Oh magic !
Also, the "first workspace" is not always the same. It can be any workspace. (I
have 4x2 workspaces).

Rarely, but it happens, it's not the up-panel but one of my two bottom panels
that disappear.

Steps to reproduce:
1. There's no way to really reproduce this...

Actual results:


Expected results:


Does this happen every time?
no.. it happens every long enough session

Other information:
I realize that this bug report is one of the worst I ever posted : a BIG bug,
that really block the user but that cannot be reproduced...

1) I've upgraded from Hoary to Breezy. This bug is there since 2.11.2, but I'm
not sure.
This bug **doesn't** happen to user who are installing directly breezy or are
migrating from the default config !   ( profiles_migrated = true )

2) I'm not alone, see : http://ubuntuforums.org/showthread.php?p=283259#post283259

3) My intuition tell me that this bug is related to non-gnome application
playing with the notification area. I _think_  it happens when
hidding/displaying psi or amule (gtk1 compiled) from the notification area.
Maybe there's nothing related.