The ATO advises that the release of Access Manager scheduled for March 2012 has been delayed. Agents should continue to use Online Access Manager until further notice. Online Access Manager (OAM), is used to manage access and permissions for ATO online services, including the Tax Agent, BAS Agent and Business Portals. It is intended that OAM will be replaced with a new standalone system - Access Manager (AM).
For more information about the changes, go here