(warty) gnome-panel crash on login

[toyfactory]

Just now Gnome-panel crashed, and kept crashing.  I hit Ctrl-Alt-
Backspace and tried to log in again, same problem.  I hit Ctrl-Alt-
Backspace and restarted, same problem when I try to log back in.

I don't know what I did to cause this problem, other than successfully
installing the xchm file viewer using Synaptic, and unsuccessfully
attempting to copy a Firefox Internet shortcut from the desktop to a
mounted vfat drive. Gnome is now unusable so for the time being it's
back to Windows (which incidentally feels a good deal more responsive
than Gnome).

I've tried to remove and reinstall gnome-panel using the 'safe-mode'
login but it hasn't solved the problem.  Is there anything else I should
try to reinstall or are there any configuration files that might have
gotten mangled?

Thanks again for your help,

Nick