As topic, when set render to Region, it will terminate during(or right before) Secondary GI (Set to UHD default state).
"4/10/2015 8:33:49 AM; CORONA: Computing secondary GI
4/10/2015 8:33:51 AM; An unexpected exception has occurred in the network renderer and it is terminating.
4/10/2015 8:33:51 AM; Error rendering frame 0: An unexpected exception has occurred in the network renderer and it is terminating."