gnome does not start properly any more

[Evgeny <evgen ibqn googlemail com>]

Hallo List,
I am looking for a solution for my strange situation:
once upon a time gnome desktop environment stopped to launch itself
properly...

i.e. an empty desktop with a background image appears. panels, desktop
icons are not present. 10-30 secs later a mouse pointer appear with a
pop-up window without borders with an error message:
"No system tray detected on this system. Unable to start, exiting.".
after clicking on OK button, mouse pointer turns into a black X and does
not react any more.

here is the output of the xsession-errors file:
##########################################################################
$ cat ~/.xsession-errors
/etc/gdm/Xsession: Beginning session setup...
Setting IM through im-switch for locale=de_DE.
Start IM through /home/mariya/.xinput.d/de_DE linked
to /etc/X11/xinit/xinput.d/none.
gnome-session[1027]: WARNING: No required applications specified
GNOME_KEYRING_CONTROL=/tmp/keyring-cyyPsN
GNOME_KEYRING_PID=1123
GNOME_KEYRING_CONTROL=/tmp/keyring-cyyPsN
SSH_AUTH_SOCK=/tmp/keyring-cyyPsN/ssh
GNOME_KEYRING_CONTROL=/tmp/keyring-cyyPsN
SSH_AUTH_SOCK=/tmp/keyring-cyyPsN/ssh

(polkit-gnome-authentication-agent-1:1146): GLib-GObject-WARNING **:
cannot register existing type `_PolkitError'

(polkit-gnome-authentication-agent-1:1146): GLib-CRITICAL **:
g_once_init_leave: assertion `initialization_value != 0' failed
** (nm-applet:1145): DEBUG: old state indicates that this was not a
disconnect 0

(gnome-power-manager:1141): GLib-GObject-WARNING
**: /build/buildd/glib2.0-2.24.1/gobject/gsignal.c:2273: signal
`proxy-status' is invalid for instance `0x9321838'

** (gnome-power-manager:1141): WARNING **: Either HAL or DBUS are not
working!

** (gnome-power-manager:1141): WARNING **: proxy failed

** (gnome-power-manager:1141): WARNING **: failed to get Computer root
object

** (gnome-power-manager:1141): WARNING **: proxy NULL!!

(gnome-power-manager:1141): GLib-GObject-WARNING **: value "-nan" of
type `gdouble' is invalid or out of range for property `percentage' of
type `gdouble'

(gnome-power-manager:1141): GLib-GObject-WARNING **: value "-nan" of
type `gdouble' is invalid or out of range for property `percentage' of
type `gdouble'

(gnome-power-manager:1141): GLib-GObject-WARNING **: value "-nan" of
type `gdouble' is invalid or out of range for property `percentage' of
type `gdouble'

(gnome-power-manager:1141): GLib-GObject-WARNING **: value "-nan" of
type `gdouble' is invalid or out of range for property `percentage' of
type `gdouble'
** (nm-applet:1145): DEBUG: foo_client_state_changed_cb
/usr/lib/pymodules/python2.6/gtk-2.0/gtk/__init__.py:127:
RuntimeWarning: PyOS_InputHook is not available for interactive use of
PyGTK
  set_interactive(1)
** (nm-applet:1145): DEBUG: foo_client_state_changed_cb

** (gnome-settings-daemon:1125): CRITICAL **: setup_bg: assertion
`manager->priv->bg == NULL' failed
evolution-alarm-notify-Message: Setting timeout for 50292 1275775200
1275724908
evolution-alarm-notify-Message: Sun Jun 6 00:00:00 2010

evolution-alarm-notify-Message: Sat Jun 5 10:01:48 2010

** (update-notifier:1443): DEBUG: Skipping reboot required
error: No system tray detected on this system. Unable to start, exiting.
##########################################################################

1. however, keybord works, so I am able to switch to tty terminal and
from there I am able manually start gnome-panel, nautilus and metacity
(to get border and friends) with DISPLAY=:0.0 <app-name>

2. I checked to ensure, that the file system is ok, by creating/touching
a file /forcefsck

actually, I do no believe .xsession-errors file is relevant here. 
I use ubuntu 10.04 (clean install) and I think some of the issues mentioned 
where will appear on ubuntu installs ... 

I strongly believe, that my loading issue is due to some configuration file/s
(because I had a similar story due to a power failure, but it's another story), 
which interrupts a gnome launching process, but I have absolutely not idea, 
where to look this time...



regards Evgen