dbus stops responding during autopilot tests

At some point during autopilot tests, dbus stops responding then X uses 100% CPU and the test session cannot finish.

You'll find in attachment the home directory of the guest session used to run the tests.
~/ap.log contains the output of autopilot

In .cache/upstart/dbus.log I noticed the following line around the same time dbus stopped responding:
 (process:2239): dee-CRITICAL **: Unable to get value. NULL row data in DeeSequenceModel@0x1bcdce0 at position 2. The row has probably been removed
 (process:2239): dee-CRITICAL **: Unable to get boolean. Column 7 in DeeSequenceModel@0x1bcdce0 holds a NULL value in row 2

I don't know if it's related, the cause or the symptom of the problem.

dbus stopped responding at "test unity.tests.launcher.test_switcher.LauncherSwitcherTests.test_launcher_switcher_cancel (Single Monitor)" This is the first test where the message "DBusException: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken. appears"

TEST CASE:
autopilot run -v unity

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: unity 7.0.0daily13.06.07-0ubuntu1
ProcVersionSignature: Ubuntu 3.9.0-4.9-generic 3.9.4
Uname: Linux 3.9.0-4-generic x86_64
ApportVersion: 2.10.2-0ubuntu1
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
Date: Mon Jun 10 15:31:02 2013
InstallationDate: Installed on 2012-10-25 (227 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MarkForUpload: True
SourcePackage: unity
UpgradeStatus: Upgraded to saucy on 2012-12-02 (189 days ago)