Comment 5 for bug 136529

Finally did some debugging.

I've tried removing xserver-gl (which removed /etc/X11/Xsession.d/98xserver-xgl_start-server) - no change.
I've tried commenting out gpg-agent (no change).

My .xsession-errors:
(process:17990): Gtk-WARNING **: This process is currently running setuid or setgid.
This is not a supported use of GTK+. You must create a helper
program instead. For further details, see:

    http://www.gtk.org/setuid.html

Refusing to initialize GTK+.

(process:17994): Gtk-WARNING **: This process is currently running setuid or setgid.
This is not a supported use of GTK+. You must create a helper
program instead. For further details, see:

    http://www.gtk.org/setuid.html

Refusing to initialize GTK+.
/etc/gdm/Xsession: Beginning session setup...

And the all inportant strace I'll attach :-) (strace -e trace=process -f -p (2nd gdm process))
The exec's are both referring to "/usr/bin/gdmflexiserver" which isn't itself setuid

17982 execve("/usr/bin/gnome-keyring-daemon", ["/usr/bin/gnome-keyring-daemon", "-d"], [/* 51 vars */]) = 0
17984 clone(child_stack=0xb7b494c4, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0xb7b49bd8, {entry_number:6, base_addr:0xb7b49b90, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}, child_tidptr=0xb7b49bd8) = 17986
17988 execve("/etc/gdm/PreSession/Default", ["/etc/gdm/PreSession/Default"], [/* 59 vars */]) = 0
17990 execve("/usr/bin/gdmflexiserver", ["gdmflexiserver", "--command=GET_CONFIG greeter/Gra"...], [/* 59 vars */]) = 0
17993 execve("/bin/sed", ["sed", "s/^\\([^ ]*\\) .*$/\\1/"], [/* 59 vars */]) = 0
17994 execve("/usr/bin/gdmflexiserver", ["gdmflexiserver", "--command=GET_CONFIG greeter/Bac"...], [/* 59 vars */]) = 0
17995 execve("/usr/bin/xsetroot", ["/usr/bin/xsetroot", "-cursor_name", "left_ptr", "-solid", "#dab082"], [/* 59 vars */]) = 0
17987 execve("/etc/gdm/Xsession", ["/etc/gdm/Xsession", "/usr/bin/gnome-session"], [/* 19 vars */]) = 0