Error Message:

The quorum log checkpoint could not be restored to the cluster database. There may be open handles to the cluster database that prevent this operation from succeeding.

Explanation:

This error occurs when you try either to have a server join a cluster or to bring an application online. When a server joins an existing cluster, it downloads the entire cluster database from the node already in the cluster. Failure of the operation means another application has the HKEY_LOCAL_MACHINE\Cluster key open. An attempt to bring an individual application online can fail for the same reason: Another application has a handle open to the registry key that the application you're bringing online needs to update.

User Action:

Close all other applications, and try the operation again (whether joining the cluster or bringing the application online).