I've been trying to setup a simple replication system. 1 main mongo, 1 backup, and 1 arbiter.

Unfortunately, firing it up lead to main being elected SECONDARY, and the backup being elected PRIMARY.

Main priority set to 100, and backup a priority of 0, along with a slave delay of 3600.

Downing backup leads to main being elected PRIMARY, but when backup is brought back on line, it resumes its spot as PRIMARY. Main then enters RECOVERING mode, and never recovers.

hidden = true has no effect on this behaviour.

More details including various config files:

http://stackoverflow.com/questions/8858831/trying-to-setup-mongo-replication-but-end-up-with-two-secondary-members-and-no/8858940#8858940

This was eventually solved by reinstalling all of the relevant servers.