Firefox complains while running, occasionally locks system at start

[stan]

Hi,

If I run Firefox 3.5 on F11 x86_64 from a terminal as
/usr/bin/firefox &
the following messages come up on the terminal continuously:

(firefox:20872): GLib-GObject-WARNING **: IA__g_object_weak_unref:
couldn't find weak ref 0x3edb469920(0x7f599462e1e0)

(firefox:20872): GLib-GObject-WARNING **: IA__g_object_weak_unref:
couldn't find weak ref 0x3edb469920(0x7f5993982fa0)

Occasionally, while starting, it locks the system completely.

Bug in glibc? gtk? firefox?