Hi,
Have done any changes to vCenter server certificate ?
I see this error message
2013-01-06T00:15:29.926-06:00 [02772 error '[SSO][SsoAdminFacadeImpl]'] [RefreshSsoToken] AcquireToken exception: Authentication failed: Authentication failed
2013-01-06T00:15:29.926-06:00 [02772 info '[SSO]'] [UserDirectorySso] GetUserInfo NormalizationException: RemoteGetDomainNames RuntimeServiceFault exception: sso.fault.RuntimeServiceFault
2013-01-06T00:15:29.926-06:00 [02772 error '[SSO]'] [UserDirectorySso] NormalizeUserName AuthException: Authorize Exception
2013-01-06T00:15:29.926-06:00 [02772 error '[SSO]'] [UserDirectorySso] GetDefaultPrincipal AuthException: Authorize Exception
If you have made any changes revert it back issue should get resolved.
Regards
Mohammed