Launchers Not Working

[rgheck]

For a little while now, I've been getting this error:

kdeinit4: preparing to launch /usr/bin/firefox

Gdk-ERROR **: The program 'firefox' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadWindow (invalid Window parameter)'.
   (Details: serial 9502 error_code 3 request_code 20 minor_code 0)
   (Note to programmers: normally, X errors are reported asynchronously;
    that is, you will receive the error a while after causing it.
    To debug your program, run it 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.)
aborting...
/usr/lib64/firefox-3.5.4/run-mozilla.sh: line 131: 20670 Aborted 
          "$prog" ${1+"$@"}

sometimes, when trying to launch Firefox via a launcher in the panel. I 
do not get it when launching from a terminal. I also see the same 
problem with Thunderbird.

Any ideas?

Richard