qdii@ciruella ~ $ gdb --args /usr/bin/gnome-panel-renamed --sync
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Reading symbols from /usr/bin/gnome-panel-renamed...(no debugging symbols found)...done.
(gdb) break gdk_x_error
Function "gdk_x_error" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (gdk_x_error) pending.
(gdb) r
Starting program: /usr/bin/gnome-panel-renamed --sync
[Thread debugging using libthread_db enabled]
[New Thread 0x7fffec82a700 (LWP 5956)]
[New Thread 0x7fffdc6dc700 (LWP 5962)]
The program 'gnome-panel' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
  (Details: serial 2032 error_code 8 request_code 7 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.)
[Thread 0x7fffec82a700 (LWP 5956) exited]
[Thread 0x7fffdc6dc700 (LWP 5962) exited]

Program exited with code 01.
(gdb)