have the following problem : For a project I've tentatively created a Silverlight 5 web application and successfully integrated a WCF service. So far so good , in the Visual Studio 2012 environment everything works as intended. The data is processed. Now I wanted to see if it all works well on IIS 7.5 . When I called the test page and spoke to the WCF service Error 405 - Method not allowed occures. After searching I solved the problem with a module allocation for *.svc .                       So, then comes the error 405 although no longer , and the service also reports the status 200 - OK . Unfortunately, the application still does not work . Now this error is reported in Silverlight : The server doenst reply a meaningful response , which may be caused by a non- matching agreement , a premature session shutdown or an internal server error . No idea what I must adjust or change now. Have read on one of the few sites on the topic that is ClientConfig blame, as they would continue as a reference for the *.xap file is valid after publishing , and not used WebConfig ... But according to the error message above, it seems to be problem in the ServiceModel.dll ... Please , can anyone help me resolve this error? Thank you, Roland I uploaded my project. Maybe someone can solve the issues in there or can check my config-files. http://www.file-upload.net/download-8261762/CiFls.zip.html