weird glib2 pthread error

[Thomas Klausner <wiz%NetBSD.org@localhost>]

After updating my packages, thunderbird and pan do not reliably start
on 6.99.10/amd64.

Sometimes I see:
(pan:9516): GLib-ERROR **: file gthread-posix.c: line 1128 
(g_system_thread_new): error 'Unknown error: 4294967295' during 'pthread_create'
(thunderbird:19762): GLib-ERROR **: file gthread-posix.c: line 1128 
(g_system_thread_new): error 'Unknown error: 4294967295' during 'pthread_create'

The backtrace for the thunderbird core dump is:
#0  0x00007f7febe47e85 in g_logv () from /usr/pkg/lib/libglib-2.0.so.0
#1  0x00007f7febe4801c in g_log () from /usr/pkg/lib/libglib-2.0.so.0
#2  0x00007f7febe796d0 in g_system_thread_new () from 
/usr/pkg/lib/libglib-2.0.so.0
#3  0x00007f7febe620ab in g_thread_new_internal () from 
/usr/pkg/lib/libglib-2.0.so.0
#4  0x00007f7febe62167 in g_thread_new () from /usr/pkg/lib/libglib-2.0.so.0
#5  0x00007f7fe8ab5d96 in ?? () from /usr/pkg/lib/libgio-2.0.so.0
#6  0x00007f7fe8aaac57 in ?? () from /usr/pkg/lib/libgio-2.0.so.0
#7  0x00007f7fe8aab2ac in g_bus_get_sync () from /usr/pkg/lib/libgio-2.0.so.0
#8  0x00007f7fdd6145c6 in gconf_get_server () from /usr/pkg/lib/libgconf-2.so.4
#9  0x00007f7fdd614816 in gconf_activate_server () from 
/usr/pkg/lib/libgconf-2.so.4
#10 0x00007f7fdd61ce3d in gconf_get_config_server () from 
/usr/pkg/lib/libgconf-2.so.4
#11 0x00007f7fdd61d5ce in gconf_engine_connect () from 
/usr/pkg/lib/libgconf-2.so.4
#12 0x00007f7fdd61d7e2 in gconf_engine_get_database.clone.5 () from 
/usr/pkg/lib/libgconf-2.so.4
#13 0x00007f7fdd61df6d in gconf_engine_notify_add () from 
/usr/pkg/lib/libgconf-2.so.4
#14 0x00007f7fdd624d12 in gconf_client_add_dir () from 
/usr/pkg/lib/libgconf-2.so.4
#15 0x00007f7fe2a512bf in ?? () from /usr/pkg/lib/libgnomeui-2.so.0
#16 0x00007f7fe1a0d0ed in gnome_program_postinit () from 
/usr/pkg/lib/libgnome-2.so.0
#17 0x00007f7fe1a0d4d2 in ?? () from /usr/pkg/lib/libgnome-2.so.0
#18 0x00007f7fe1a0d713 in gnome_program_initv () from 
/usr/pkg/lib/libgnome-2.so.0
#19 0x00007f7fe1a0d7ee in gnome_program_init () from 
/usr/pkg/lib/libgnome-2.so.0
#20 0x00007f7ff1d85954 in ?? () from /usr/pkg/lib/thunderbird/libxul.so
#21 0x00007f7ff1d7daba in ?? () from /usr/pkg/lib/thunderbird/libxul.so
#22 0x00007f7ff1d7fb66 in ?? () from /usr/pkg/lib/thunderbird/libxul.so
#23 0x00007f7ff1d7fddf in XRE_main () from /usr/pkg/lib/thunderbird/libxul.so
#24 0x0000000000401cf0 in _start ()

The one for pan is shorter:
(gdb) bt
#0  0x00007f7ff1047e85 in g_logv () from /usr/pkg/lib/libglib-2.0.so.0
#1  0x00007f7ff104801c in g_log () from /usr/pkg/lib/libglib-2.0.so.0
#2  0x00007f7ff10796d0 in g_system_thread_new () from 
/usr/pkg/lib/libglib-2.0.so.0
#3  0x00007f7ff10620ab in g_thread_new_internal () from 
/usr/pkg/lib/libglib-2.0.so.0
#4  0x00007f7ff106242e in ?? () from /usr/pkg/lib/libglib-2.0.so.0
#5  0x00007f7ff1062863 in g_thread_pool_new () from 
/usr/pkg/lib/libglib-2.0.so.0
#6  0x00000000005a6830 in pan::WorkerPool::WorkerPool(int, bool) ()
#7  0x000000000047957d in main ()

I've tried thunderbird a few times in a row, and it always failed, but
pan started on the second try.
Now thunderbird might also start but doesn't due to a different error:
###!!! ABORT: JS_NewRuntime failed.: file 
/scratch/mail/thunderbird/work/comm-release/mozilla/js/xpconnect/src/XPCJSRuntime.cpp,
 line 2005
###!!! ABORT: JS_NewRuntime failed.: file 
/scratch/mail/thunderbird/work/comm-release/mozilla/js/xpconnect/src/XPCJSRuntime.cpp,
 line 2005


I have glib2-2.32.4 and a 6.99.10/amd64 snapshot from 20120809.

Any ideas?
 Thomas