Hi I have an application that works fine in my dev enviroment, but throws weird errors in the production enviroment, I checked the version of .net on my dev machine aswell as the production server , they both run 3.5.30729.01. The exception I get is a System.IO.FileNotFoundException. StackTrace: at System.Diagnostics.FileVersionInfo.GetVersionInfo(String fileName) at System.Configuration.ClientConfigPaths.SetNamesAndVersion(String applicationFilename, Assembly exeAssembly, Boolean isHttp) at System.Configuration.ClientConfigPaths..ctor(String exePath, Boolean includeUserConfig) at System.Configuration.ClientConfigPaths.GetPaths(String exePath, Boolean includeUserConfig) at System.Configuration.ClientConfigurationHost.get_ConfigPaths() at System.Configuration.ClientConfigurationHost.RequireCompleteInit(IInternalConfigRecord record) at System.Configuration.BaseConfigurationRecord.GetSectionRecursive(String configKey, Boolean getLkg, Boolean checkPermission, Boolean getRuntimeObject, Boolean requestIsHere, Object& result, Object& resultRuntimeObject) at System.Configuration.BaseConfigurationRecord.GetSection(String configKey) at System.Configuration.ClientConfigurationSystem.System.Configuration.Internal.IInternalConfigSystem.GetSection(String sectionName) at System.Configuration.ConfigurationManager.GetSection(String sectionName) at System.Configuration.PrivilegedConfigurationManager.GetSection(String sectionName) at System.DirectoryServices.SearchResultCollection.ResultsEnumerator..ctor(SearchResultCollection results, String parentUserName, String parentPassword, AuthenticationTypes parentAuthenticationType) at System.DirectoryServices.SearchResultCollection.GetEnumerator() at System.DirectoryServices.DirectorySearcher.FindOne() Yesterday the error just went away, and today the error is occuring again. I tried using reflector and it appears to have something to do with config files or user config files. any ideas?