I have two NW6.5SP7 servers that are used as password change portals
(using the http://servername.domain.edu/nps URL). Both servers are
using externally-signed certificates, signed by Entrust. Yesterday,
Server 1 began refusing all SSL connections with "certificate revoked".
Server 2 was fine.

Today Server 1 magically recovered and works fine again. Before I
return it to service, are there any logs I can examine to find out what
happened, so it doesn't happen again?