Thanks for the follow-up, Noah.
Originally Posted by noah++
Only thing I've found of interest is
in /var/log/syslog, prior to the reboot. I've located that elsewhere in the logs, incl. areas that don't seem to have resulted in me rebooting. There is an Xorg.log.0.old with a timestamp that matches the hour:minute of the syslog entry with the "custom.com" error message timestamp. There's a lot of informational stuff in there. Can't tell what's important and what's not.
gdm-simple-slave: WARNING: Unable to load file '/etc/gdm/custom.conf': No such file or directory
I searched on the warning message. Inconclusive results, incl. the instance by developers that the message has no bearing on anything. Problems that seem related/associated with this continue to be reported by Ubuntu 10.x users.
The problem has not recurred since I disabled the screen saver/locker.
I think you misread my issue. The problem isn't that screen-locking isn't happening, it's that, sometimes, when it does, I cannot make it un-happen.
Originally Posted by karthick87