Cannot get thread event message: debugger service failed

["D. Hugh Redelmeier" <hugh@mimosa.com>]

I'm trying to debug Firefox on Linux.  I'm using GDB.  Execution of
Firefox is frequently interrupted with this message:
  [New Thread 0x44125950 (LWP 30469)]
  Cannot get thread event message: debugger service failed
At this point, I enter a "continue" GDB command and execution
proceeds.

Sometimes the screen locks up until the "continue".  So I need to run
GDB somewhere other than the X desktop.

What is the best way to avoid this problem and get on with debugging 
Firefox?  (I admit: a quixotic quest.)

Google finds this for me:
  http://sourceware.org/ml/gdb/2006-10/msg00259.html
but I don't see a resolution.

Some details:

- I get this message on 64-bit Fedora 9 (on a dual-core machine) and on 
  64-bit Ubuntu 8.04 (on a quad core machine)

- GDB on Fedora 9: gdb-6.8-23.fc9.x86_64

- GDB on Ubuntu 8.04: 6.8-1ubuntu3


- I run Firefox this way: Firefox --sync
  or: Firefox --sync -no-remote

- I run gdb later, giving it the executable file and the PID

- I tell gdb to ignore sigpipe signals: handle SIGPIPE nostop

- I then let GDB continue Firefox

- after a small amount of browsing, the dreaded message shows up