Gnome session manager disappears when updating FC6

[Andrew Wood]

Hi,

I've just run a software update on FC6. When I reboot and log in then
the gnome window manager has been replaced by TWM. This was something of
a shock although I have enough knowledge to realise what had happened.
(I can't see why it happened though, other than saying there's a bug in
the update). It has undermined my confidence in Fedora as a stable
release somewhat.

Looking at Linux answers then I found a suggestion to run: yum install
gnome-session. This worked in bringing up gnome, which I was previously
using. Unfortunately, the desktop is not quite as it was. I have a panel
appearing which says: 'The panel encountered a problem loading OAFIID:
Gnome_mixerApp Do you want to delete the applet from your config'.  A
similar error occurs for the Gnome_Panel_TrashApplet.

Any suggestions how I can restore the desktop to what it was?

Andrew, Oxford.