Flash in Firefox results in X Window System Error

[Dennis Jacobfeuerborn]

After upgrading the X11 libraries in Fedora Core Rawhide yesterday Firefox 
now crashes with a "X Window System Error" everytime I load a page 
containing a flash applet:

Gdk-ERROR **: The program 'Gecko' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
   (Details: serial 120 error_code 8 request_code 146 minor_code 3)
   (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...

More details (backtrace,talkback incident link) in this Red Hat Bugzilla 
report: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=194604

What is the proper way to decode the error numbers above into something 
human readable?

Regards,
   Dennis