I have many times the following message in my .xsession-errors file that appear at anything that start at login in mate 
** (mate-session:8447): WARNING **: Couldn't connect to accessibility bus: Failed to connect to socket /tmp/dbus-LUmiFVwa0k: Connection refused
Replace mate-session:nnn by the process name and jobid for each thing started at the beginning of a session.
Anybody have this problem ?
Is that something related to "consolekit" or a bad environment variable setting somewhere ?
Regards,
Bernard