Yes, this is a post-SP1 update for SQL Server 2005 (available for public download). I have to look twice to make sure I wasn't seeing things! It includes fixes which didn't make the SP1 cut-off point.
Go here for more information: http://support.microsoft.com/kb/918222
I really should keep a closer eye on those SQL Server knowledge base RSS feeds! There are two new SQL Server 2000 Post SP4 hotfix rollup packages available both for the Database Engine and Analysis Services.
You can get them here:
Hotfix rollup package for SQL Server 2000 Analysis Services Service Pack 4 Build 2174 http://support.microsoft.com/kb/907323
A cumulative hotfix package is available for SQL Server 2000 Service Pack 4 build 2187 http://support.microsoft.com/kb/916287