I've been working on a little Silverlight utility which calls a Silverlight web service. It works from my dev machine (XPsp2). I've tried publishing it to a 2008 R2 IIS 7.5 server and it doesn't work when trying to contact the web service. So I've tried using the WcfTestClient to connect to the web service. That gave an error. So I turned off CustomErrors and used IE and I get the following. Any idea why? There's no App_Code folder in the app.

Failed to map the path '/app42/App_Code/'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: Failed to map the path '/app42/App_Code/'.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[InvalidOperationException: Failed to map the path '/app42/App_Code/'.]
   System.Web.Configuration.ProcessHostConfigUtils.MapPathActual(String siteName, VirtualPath path) +320
   System.Web.Configuration.ProcessHostServerConfig.System.Web.Configuration.IServerConfig.MapPath(IApplicationHost appHost, VirtualPath path) +34
   System.Web.Hosting.MapPathBasedVirtualPathEnumerator..ctor(VirtualPath virtualPath, RequestedEntryType requestedEntryType) +169
   System.Web.Hosting.MapPathBasedVirtualPathCollection.System.Collections.IEnumerable.GetEnumerator() +43
   System.Web.Compilation.CodeDirectoryCompiler.ProcessDirectoryRecursive(VirtualDirectory vdir, Boolean topLevel) +147
   System.Web.Compilation.CodeDirectoryCompiler.GetCodeDirectoryAssembly(VirtualPath virtualDir, CodeDirectoryType dirType, String assemblyName, StringSet excludedSubdirectories, Boolean isDirectoryAllowed) +11196502
   System.Web.Compilation.BuildManager.CompileCodeDirectory(VirtualPath virtualDir, CodeDirectoryType dirType, String assemblyName, StringSet excludedSubdirectories) +185
   System.Web.Compilation.BuildManager.CompileCodeDirectories() +654
   System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled() +658

[HttpException (0x80004005): Failed to map the path '/app42/App_Code/'.]
   System.Web.Compilation.BuildManager.ReportTopLevelCompilationException() +76
   System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled() +1012
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters) +1025

[HttpException (0x80004005): Failed to map the path '/app42/App_Code/'.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +11301302
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +88
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +4338644

Version Information: Microsoft .NET Framework Version:2.0.50727.4927; ASP.NET Version:2.0.50727.4927