Aha, looking in the syslog I see lots of the following:
Sep 20 14:49:13 zentyal kernel: [171376.751775] init: ebox.loggerd main process (52828) terminated with status 9
Sep 20 14:49:13 zentyal kernel: [171376.751795] init: ebox.loggerd main process ended, respawning
Sep 20 14:49:25 zentyal kernel: [171389.199573] init: ebox.loggerd main process (52846) terminated with status 9
Sep 20 14:49:25 zentyal kernel: [171389.199593] init: ebox.loggerd main process ended, respawning
Sep 20 14:49:38 zentyal kernel: [171401.677225] init: ebox.loggerd main process (52954) terminated with status 9
Sep 20 14:49:38 zentyal kernel: [171401.677246] init: ebox.loggerd main process ended, respawning
Sep 20 14:49:50 zentyal kernel: [171414.103164] init: ebox.loggerd main process (52987) terminated with status 9
Sep 20 14:49:50 zentyal kernel: [171414.103189] init: ebox.loggerd main process ended, respawning
Sep 20 14:50:03 zentyal kernel: [171426.587614] init: ebox.loggerd main process (53008) terminated with status 9
Sep 20 14:50:03 zentyal kernel: [171426.587637] init: ebox.loggerd main process ended, respawning
Sep 20 14:50:15 zentyal kernel: [171439.099930] init: ebox.loggerd main process (53118) terminated with status 9
Sep 20 14:50:15 zentyal kernel: [171439.099958] init: ebox.loggerd main process ended, respawning
Sep 20 14:50:28 zentyal kernel: [171451.576796] init: ebox.loggerd main process (53372) terminated with status 9
Sep 20 14:50:28 zentyal kernel: [171451.576825] init: ebox.loggerd main process ended, respawning
Sep 20 14:50:40 zentyal kernel: [171464.030033] init: ebox.loggerd main process (53454) terminated with status 9
Sep 20 14:50:40 zentyal kernel: [171464.030054] init: ebox.loggerd main process ended, respawning
Sep 20 14:50:53 zentyal kernel: [171476.522623] init: ebox.loggerd main process (53499) terminated with status 9
Sep 20 14:50:53 zentyal kernel: [171476.522643] init: ebox.loggerd main process ended, respawning
Sep 20 14:51:05 zentyal kernel: [171488.980299] init: ebox.loggerd main process (53516) terminated with status 9
Sep 20 14:51:05 zentyal kernel: [171488.980321] init: ebox.loggerd main process ended, respawning
Sep 20 14:51:18 zentyal kernel: [171501.407468] init: ebox.loggerd main process (53597) terminated with status 9
Sep 20 14:51:18 zentyal kernel: [171501.407489] init: ebox.loggerd main process ended, respawning
Sep 20 14:51:30 zentyal kernel: [171513.916003] init: ebox.loggerd main process (53616) terminated with status 9
Sep 20 14:51:30 zentyal kernel: [171513.916024] init: ebox.loggerd main process ended, respawning
Sep 20 14:51:43 zentyal kernel: [171526.343189] init: ebox.loggerd main process (53702) terminated with status 9
Sep 20 14:51:43 zentyal kernel: [171526.343210] init: ebox.loggerd main process ended, respawning
Sep 20 14:51:55 zentyal kernel: [171538.805120] init: ebox.loggerd main process (53734) terminated with status 9
Sep 20 14:51:55 zentyal kernel: [171538.805144] init: ebox.loggerd main process ended, respawning
Sep 20 14:52:08 zentyal kernel: [171551.268769] init: ebox.loggerd main process (53758) terminated with status 9
Sep 20 14:52:08 zentyal kernel: [171551.268792] init: ebox.loggerd main process ended, respawning
Sep 20 14:52:20 zentyal kernel: [171563.730357] init: ebox.loggerd main process (53841) terminated with status 9
Sep 20 14:52:20 zentyal kernel: [171563.730378] init: ebox.loggerd main process ended, respawning
Sep 20 14:52:33 zentyal kernel: [171576.327033] init: ebox.loggerd main process (53900) terminated with status 9
Sep 20 14:52:33 zentyal kernel: [171576.327052] init: ebox.loggerd main process ended, respawning
Any clues as to what 'status 9' means?