Applicable to OS X Server 10.7.5.
The Server Alerts logs can get corrupted and when it does Server.app will not be able to load it. CPU usage will increase and use a lot of the available resources. The processing ball spins forever or sometimes ends with an “Error Reading” alert.
Server Alerts are logged by emond directly to the ASL events database, and are stored in /var/log/eventmonitor . Deleting the log will clear the problem.
sudo rm -rf /var/log/eventmonitor/*
to remove the events ASL database, then quit and re-open Server.app.
A new events database is recreated after deleting the contents of the eventmonitor folder and opening Server.app again. Server Alerts functions normally and logging resumes after clearing the existing database files.