Thank you for reporting this to Ubuntu. Could you please generate an apport
crash report for this?
You can enable apport for one instance like this:
sudo service apport start force_start=1
I am marking this invalid as apport will open a new bug when the crash
is generated. If it does not, you can
** Attachment added: "Dependencies.txt"
http://launchpadlibrarian.net/37507664/Dependencies.txt
** Attachment added: "ExtensionSummary.txt"
http://launchpadlibrarian.net/37507665/ExtensionSummary.txt
** Attachment added: "XsessionErrors.txt"
http://launchpadlibrarian.net/37507666/Xsessi