A pool of account-identifiers (RIDs) has been invalidated. This may occur in the following expected cases: 1. A domain controller ...

A pool of account-identifiers (RIDs) has been invalidated. This may occur in the following expected cases:
1. A domain controller is restored from backup. 
2. A domain controller running on a virtual machine is restored from snapshot. 
3. An administrator has manually invalidated the pool. 
See http://go.microsoft.com/fwlink/?LinkId=226247 for more information.