X Window System error

[Peter Lesterhuis]

Hi,
On one of my machines I did an upgrade from f8 to f9.
After rebooting and logging in the new desktop background appears but 
without the usual icons (user's home, Trash, computer, etc).
When I try to start an application nothing happens. When I start firefox 
from the command line I get this error:

"$firefox
The program 'firefox' received an X Window System error.
This probably reflects a bug in the program. The error was 'BadName 
(named color or font does not exist)'.
(Details: serial 862 error_code 15 request_code 45 minor_code 0)
(Note to programmers: normally, X errors are reported asynchronously; 
that is, you will receive an error a while after causing it.
To debug your program, run in with the --sync command line option to 
change this behavior. You can then get a meaningful backtrace from your 
debugger if you break on the gdk-x-error() function.)"

When I try to start other applications I get similar errors.
The X-server is running. Dmesg or /var/log/messages don't give me any 
clues. Can anyone help me with this?
Peter