vCenter 5.1 SSO: A General System Error Occurred: Authorize Exception

Experienced this issue a month or so back (ended up logging a call with VMware to get confirmation of what happened) and it occurred again today so figured it was worth posting about. If you receive the following error when attempting to log into vCenter 5.1 with an AD account: A general system error occurred: Authorize Exception there are a number of potential issues. however most likely it is related to SSO and one of the Identity Sources.