Resolution:
ERROR MESSAGE:  Repository server software problem (repeated unknown/expired keys: possible client/repserver clock synchronization problem).

CIRCUMSTANCES:  Whenever a client tries to be authorized against the Repository Server.

CAUSE:  Occurs when the client host and server host clocks are not within 10 minutes of each other.
The client authorization token is only good while being within 10 minutes of login, so the server interprets the time difference as an expired authorization.

SOLUTION: Ensure date and timezone on each machine are within 10 minutes.