On July 15th, 2008 Microsoft announced the availability of the Infrastructure Update for Office Servers. The Infrastructure Update for Office Servers is a set of updates to improve platform performance and contain several customer driven fixes.  The updates are applicable to Microsoft Office SharePoint Server 2007, Windows SharePoint Services 3.0, Microsoft Search Server 2008 & Microsoft Search Server 2008 Express, Microsoft Office Project Server 2007 and Microsoft Office Project 2007.

See the official project blog for all the information:

http://blogs.msdn.com/project/archive/2008/07/15/announcing-the-infrastructure-update-for-office-servers.aspx