Gnome-Panel and Nautilus errors on startup

[Joona I Palaste <palaste cc helsinki fi>]

I've recently upgraded Gnome-Desktop, Gnome-Panel and Nautilus to 2.4
versions. Now when I start up Gnome, the component initialisation only
goes halfway through (the last two components to get initialised are
the panel and Nautilus, then it stops), and I get the following error
messages:

There was a problem registering the panel with the bonobo-activation server.
The error code is: 1078774059
The panel will now exit.

Nautilus can't be used now, due to an unexpected error from Bonobo when
attempting to register the file manager view server.

The panel eventually starts up all OK, but I am left with a desktop that
is stuck in the default settings. I can't edit any desktop preferences.
I can't even find an option to edit any desktop preferences. The closest
I have come to editing the preferences is right-click the desktop
background, choose "Change desktop background" from the popup menu, and
then select a different background. Selecting a different background has
no effect, the background stays the same.

I have obviously messed up something, but what? How can I resolve this
mess, short of reinstalling the entire Linux distribution?

I can provide more detailed information about any components if needed.

-- 
/--Joona Palaste-------------------------------------------------------\
\----------------------------------------------palaste cc helsinki fi--/