One of the guys upstairs in the consultant's bullpen has been tracking down an issue with WCF, in which the proxy does not generate correctly; specifically, it inserts an incorrect URL for the service, which results in 404 errors until the Web.config is corrected. I did a little tracking, and found what may be a partial solution . More weirdness: http://www.dasblonde.net/2008/04/24/MyProxyWrapperAndTheEVILSUOFile.aspx