menu disappeared from ubuntu 12.04 system tray

["pauriem gmail com" <pauriem gmail com>]

network manager was pre-installed with ubuntu 12.04 on my laptop and
was accessible from my top panel system tray on the desktop until
today when I rebooted after a failed install of a different package
that was trying to add itself to the system tray area also

now the network manager menu icon is gone from the tray though other
icons such as battery and messaging are still there

I can get nm-applet to show up but this is not the same

the applet area is further left, the applet menu renders in a way that
clashes with the user theme, and it is impossible to use the keyboard
to navigate to the applet

by contrast, the default network manager application was aware of the
theme and had an appearance consistent with the other dropdowns, and
it also could be entered via arrow keys from the other system tray
menus

I have spent several hours looking for documentation on what manager
is responsible for displaying these system tray application entries
(as opposed to the applets) and what resource governs the choice of
which programs get included here, but I really think I have reached a
dead end

I am wondering if you can point me to the relevant install scripts in the netw
ork manager package that might bear on this

I have already tried uninstall and reinstall of network-manager,
network-manager-gnome, gnome-panel, unity etc

if I run network manager from command line it never becomes visible
but apparently does something as a background process

thanks for any help