firefox window closes

[Thierry Chatelet <tchatelet@free.fr>]

On some click, say, to incruise the number of item you buy in a windows 
(from diferent sites), the firefox window closes. Starting firfox in a 
terminal window with the option --sync, I got the following message:

open dsp: Device or resource busy
The program 'Gecko' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadShmSeg (invalid shared segment parameter)'.
 (Details: serial 30 error_code 168 request_code 146 minor_code 2)
 (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.)

Does anyone have something similar?

I am running sid, amd64, here is the output of uname -a:
Linux lvl 2.6.17-1-amd64-k8 #1 Sat Jul 29 16:45:32 CEST 2006 x86_64 
GNU/Linux

Thierry