After logging in on an up-to-date release of Maverick the screen goes black and the error "(process:268): GLib-WARNING **: getpwuid_r(): failed due to unknown user id (0)" appears, with the mouse pointer staying on screen as the only remaining artefact of the graphical interface. The whole system freezes and it is not possible to get to a tty.
A help topic at <http://us.generation-nt.com/answer/10-4-boot-problem-glib-warning-help-197907291.html> seems to suggest that running 'sudo update-grub' helps with this problem and that it is related with the kernel update from Lucid's kernel to Maverick's. That would explain why this issue appeared between Karmic and Lucid as well.
However, I'm not sure if it makes a difference to run update-grub manually, since it must have been run before this crash when an update for the Maverick kernel was released.
I also see the
"GLib-GObject-WARNING: invalid (NULL) pointer instance
GLib-GObject-CRITICAL: g_signal_connect_data: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed"
errors in the syslog for several applications, including 'gdm-simple-greeter'. I see the same error on my other system each time I initialise a gtk.Menu object in Python with PyGTK, or when running a PyGTK application.
The last message I can find in the log files is "padlock: VIA PadLock not detected". The warning that is displayed on the screen does not appear in the syslogs.
The laptop is an Packard Bell EasyNote MZ35-V-054. Onboard graphics is a well supported ATi Radeon Xpress 200M (RC410), sound ATi IXP SB400, network RaLink RT2561/RT61.
Assigning this to the GDM package because it appears to me that it is most likely related to that.