[xmonad] xmobar disappears

[Michael Norrish]

When I restart xmonad with a M-q command my xmobar disappears.  There's an 
xmobar process running and it's not obviously blocked.  (strace shows it doing 
things, including recvfrom and writev both with non-zero positive return codes).

Xmonad also appears to think it's there in at least some sense because there's a 
strut on the top of the screen.  But instead of there being anything visible, I 
can just see the wallpaper window...

This is all under LightDM/Ubuntu12.04.  If I attempt to alter the "root window" 
(with something like display -window root some.jpg) the wallpaper doesn't 
change, suggesting that there is a wallpaper window lying on top of the "real 
root window".  Also, the wallpaper responds to right-clicks and brings up a 
gnome-config type menu.

So, perhaps my xmobar restarts underneath the wallpaper and is thus obscured.

If so, how might I bring it to the fore?

I'm running a cabal xmonad and xmobar on top of Ubuntu12.04, with an 
/usr/share/xsessions/xmonad.desktop that looks like:

   [Desktop Entry]
   Encoding=UTF-8
   Name=XMonad
   Comment=Lightweight tiling window manager
   Exec=gnome-session --session=xmonad
   Icon=xmonad.png
   Type=XSession

and a /usr/share/gnome-session/sessions/xmonad.session that looks like:

   [GNOME Session]
   Name=Xmonad session
   RequiredComponents=gnome-settings-daemon;
   RequiredProviders=windowmanager;notifications;
   DefaultProvider-windowmanager=xmonad
   DefaultProvider-notifications=notification-daemon

Thanks,
Michael