The Availability Reporting Management Pack was withdrawn from the Microsoft download site in early June due to technical problems (see may earlier post http://blogs.technet.com/cliveeastwood/archive/2006/06/02/431997.aspx).
The download site has been updated to reflect a target date on which we expect to release an updated version. See http://www.microsoft.com/downloads/details.aspx?FamilyId=8A61D369-B785-4550-BDE8-84E734EC5E40&displaylang=en
The updated text: This Management Pack has been temporarily removed pending an update. The update should be available by August 31, 2006.
The updated MP will include fixes for those problems discussed in the following KB article, http://support.microsoft.com/?id=918711, http://support.microsoft.com/?id=913278 ,http://support.microsoft.com/?id=918119, as well as an updated MP Guide, and fixes for UI connection timeout issues, MRASLoader performance issues, SQL Server 2005 installation support, amongst others.
More news on this nearer the time :)