Apple has released OS X Mountain Lion 10.8.2 Supplemental Update 2.0 for those experiencing issues with Keychain.
About OS X Mountain Lion 10.8.2 Supplemental Update 2.0
This update addresses an issue with Keychain that can affect 2012 Mac systems.
This update is recommended for all Mac systems introduced in 2012.
You can download the update from the link below...