In Debian Wheezy with accountsservice 0.6.21-6 GNOME 3 crashes  due to the patch applied in commit 5e2f077e 
lib: manage pending consolekit calls with cancellable
Pending NewSession objects can disappear just as quickly
as they appear in response to ConsoleKit signals. If
we're in the middle of talking to ConsoleKit when an
object disappears and is subsequently freed, then we'll
still try to access it from the reply callback.
This commit cancels any pending messages to the consolekit
daemon, when the session goes away.
to fix bug 50112.
It would be awesome if you could take a look. Josselin Mouette found the reason for the crash already. It would be awesome if you could suggest a fix. Thanks!
#0 0x00007f70c5ea06c9 in g_cancellable_is_cancelled (
#1 0x00007f70a7555d86 in on_get_unix_user_finished (object=<optimized out>,
result=0x4f93660, data=0x4e56240) at act-user-manager.c:1028
proxy = <optimized out>
new_session = 0x4e56240
error = 0x0
uid = <optimized out>
#2 0x00007f70c5ed93f7 in g_simple_async_result_complete (simple=0x4f93660)
current_source = 0x7f70980e4f90
current_context = 0x0
__PRETTY_FUNCTION__ = "g_simple_async_result_complete"
#3 0x00007f70c5f3177a in reply_cb (connection=<optimized out>,
res=<optimized out>, user_data=0x4f93660)
simple = 0x4f93660
value = <optimized out>
error = 0x38cfe60
fd_list = 0x2740a00
Here is a description from Josselin on how to reproduce this.
»the crash in unstable is 100% reproducible with the following : have 2 sessions open, open a 3rd one, close it, use the login prompt to switch to one of the first twos«
let's dupe this to the original report, since we already reopened it.
*** This bug has been marked as a duplicate of bug 50112 ***