http://blogs.esri.com/Support/blogs/supportcenter/archive/2009/06/25/arcgis-server-9-3-1-net-rest-services-patch.aspxIn May 2009, a patch was made available on the ESRI Support Website for ArcGIS Server .NET customers that fixed a performance problem with REST Services. It is called: “ ArcGIS (Desktop, Engine, Server) 9.3.1 REST Services Patch ” and fixed the followingenCommunityServer 2.1 SP2 (Debug Build: 61120.2)