Mac Mini Server, 2.53 GHz Intel Core 2 Duo, 4 GB RAM, Server Version 10.6.4 (fully updated).
I'm just starting to look at this strange problem. Mini server has spontaneously shut down without any warning (NB. a shutdown, not a restart). 3 times in last 3 days. The various server logs give no clues for the reason for the shutdown. All logs look totally normal prior to the required manual restart. Nothing in logs after the restart to suggest problem in any service (and I've been comparing the various service logs with other 10.6 server logs).
I note that there are no CrashReporter logs in ~/Library/Logs. Can I 'turn up' system logging temporarily somewhere? I was starting to suspect RAM but surely something would be logged somewhere?
To anyone who suspects power supply problem (as I also did), the Energy Saver preferences are set to 'Start Up Automatically after a Power Failure' and 'Restart Automatically if the Computer Freezes'. However, mini does not restart on its own. It needs physically restarted.