http://developers.de/blogs/damir_dobric/archive/2010/07/14/filenotfoundexception-invalid-impersonationlevel-amp-co.aspxWhen working with AppFabric Caching features in an application (i.E. web service) hosted in IIS, you might experience following problem: === Pre-bind state information === LOG: User = Unknown LOG: DisplayName = Microsoft.ApplicationServer.Caching.CoreenCommunityServer 2008 SP1 (Build: 30619.63)