[edgy] firefox crashes with X error

Binary package hint: firefox

Firefox is unusable, due to crashes with errors to the terminal like:
"""
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 118 error_code 8 request_code 144 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.)
"""

Strangely, I don't get the usual crash-handler dialog when this happens, it just vanishes.

This happens with some pages, not with others -- for example I can get to google.com, but a big image or complicated page (like gmail inbox) causes a crash (not reliably, but most times).

This is on a Thinkpad with integrated intel graphics. Worked fine with dapper, with the same X configuration. X config follows. This is also starting from an empty ~/.mozilla directory.