Like I said, FF is in a chroot jail (a real one).
Why is this a one-off thing? It has never done this before (and it isn't doing it now).
So far, this has been the only error that I have ever seen.
(process:2526): GLib-CRITICAL **: g_slice_set_config: assertion `sys_page_size == 0' failed
Why is this not reproduceable?