firefox crashing, what should i do

I am running Freebsd 5.3
I am using the xorg xserver
I have updated all my ports.
I have a Dell Latitude C600 (though I don't think that should matter)

I have occasional firefox crashes.  To test out what happens
when I see flash content, I went to the strong bad
http://www.homestarrunner.com site.
It kept crashing.
then i thought "I'm smart, I'll install the flash block plugin
flashblock.mozdev.org for the next time I hit flash content"
So I did.
then when I go back to the above site, same thing, boom, firefox crashes

I get this error:

The program 'firefox-bin' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadShmSeg (invalid shared segment parameter)'.
  (Details: serial 40 error_code 149 request_code 142 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.)

What am I doing wrong?

thanks.