That's the thing though, there was none (trust me I was expecting something). The only line I could find around that time was in syslog; gdm_slave_xioerror_handler: Fatal X error - Restarting :0 There was literally no other signs or explanations for the restart in any other log. Nothing contained in the gdm or Xorg logs either. In any case it's been resolved by changing to the "radeon" xserver.
