mysterious error dialog when logging into gnome 2.16.1

[Hans Nieser]

I've just updated to gnome 2.16.1 (marcuscom), but I get an error dialog
when I log into gnome. The dialog dissappears before I can read it so I
don't know what the problem is. But it's annoying nonetheless.

I've checked gdm's log, xorg's log and ~/.xsession-errors but I can't
figure out what is causing this error. Does anyone know where else to look?