Unable to find the requested .NET framework data provider. It may not be installed.

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.NET

Hi,
After reading almost all the content that can be found about this problem and trying everything that does not sound dangerous for production server i decide to post my question here with all Stack Trace info that i am getting.
Can someone advice me what to do?

Stack Trace:

[ArgumentException: Unable to find the requested .Net Framework Data Provider.  It may not be installed.]
   System.Data.Common.DbProviderFactories.GetFactory(String providerInvariantName) +1044767
   WebMatrix.Data.DbProviderFactoryWrapper.CreateConnection(String connectionString) +64
   WebMatrix.Data.<>c__DisplayClass15.<openconnectionstringinternal>b__14() +16
   WebMatrix.Data.Database.get_Connection() +19
   WebMatrix.Data.Database.EnsureConnectionOpen() +13
   WebMatrix.Data.<queryinternal>d__0.MoveNext() +67
   System.Linq.Enumerable.FirstOrDefault(IEnumerable`1 source) +121
   WebMatrix.Data.Database.QuerySingle(String commandText, Object[] args) +100
   WebMatrix.WebData.DatabaseWrapper.QuerySingle(String commandText, Object[] parameters) +14
   WebMatrix.WebData.SimpleMembershipProvider.CheckTableExists(IDatabase db, String tableName) +54
   WebMatrix.WebData.SimpleMembershipProvider.CreateTablesIfNeeded() +50
   WebMatrix.WebData.WebSecurity.InitializeMembershipProvider(SimpleMembershipProvider simpleMembership, DatabaseConnectionInfo connect, String userTableName, String userIdColumn, String userNameColumn, Boolean createTables, SimpleMembershipProviderCasingBehavior casingBehavior) +82
   WebMatrix.WebData.WebSecurity.InitializeProviders(DatabaseConnectionInfo connect, String userTableName, String userIdColumn, String userNameColumn, Boolean autoCreateTables, SimpleMembershipProviderCasingBehavior casingBehavior) +54
   WebMatrix.WebData.WebSecurity.InitializeDatabaseConnection(String connectionStringName, String userTableName, String userIdColumn, String userNameColumn, Boolean autoCreateTables, SimpleMembershipProviderCasingBehavior casingBehavior) +55
   ApniSi.AuthConfig.RegisterAuth() +47
   ApniSi.MvcApplication.Application_Start() +155

[HttpException (0x80004005): Unable to find the requested .Net Framework Data Provider.  It may not be installed.]
   System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +10093517
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +118
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +173
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +218
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +296

[HttpException (0x80004005): Unable to find the requested .Net Framework Data Provider.  It may not be installed.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +10074716
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +95
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +254

What I have tried:

I did try to set "DbProviderFactories" in the web.config but it goes with 500 error :(