http://forums.esri.com/Thread.asp?c=158&f=1702&t=242271&mc=10#762971%29.
What was happening was that a domain-level group policy was REMOVING the
"Log on as a service" and "Log on as a batch job" local policies from
the ArcSOC user. These policies are put in place by the Post-Install
and are required for the ArcSOC user to start services, among other
things.
Whenever the domain-level group policy was applied (approximately
once a day but not at any set interval), the local policies were removed
and the next time the services were recycled they would fail to
restart.
As info for others (since it does not seem to be well documented), I
have pasted the 2 local policies and the users to which they are
applied, below:
Local Policy: Log on as a batch job
Users requiring policy:
ArcGISSOC
ArcGISSOM
ArcGISWebServices
Local Policy: Log on as a service
Users requiring policy:
ArcGISSOM