Page says return code 0

HI All,

when trying to replay forum post in SF backend i face this ( error Page says return code 0 ),

and i found this exception in log file 

 The current type, Telerik.Sitefinity.Web.UrlEvaluation.IUrlEvaluator, is an interface and cannot be constructed. Are you missing a type mapping?

Hello,

Can you reproduce this with a new installation or this happens only in the current website you are using? If you have performed an upgrade recently please check the upgrade log for errors. Also make sure that all config files have the correct build version you are using.  You can check the versions in SystemConfig.config. For each application module you will see something like

<add version="7.3 5610.0" name="Forums" />

You can also try to deactivate and activate the module.  Check if you have modified forums templates (Design >> Widget templates) , because you might have added something that breaks the call to the service when we try to open "create post" window.

Regards,
Ivan Dimitrov
Telerik

i upgrade from v4 to v6 and the build number in system.config =6.0 4210, I checked the log file and found the below exception and i didn't change anything in template

---------------
Type : System.InvalidOperationException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Message : The current type, Telerik.Sitefinity.Web.UrlEvaluation.IUrlEvaluator, is an interface and cannot be constructed. Are you missing a type mapping?
Source : Telerik.Sitefinity.Utilities
Help link : 
Data : System.Collections.ListDictionaryInternal
TargetSite : Void ThrowForAttemptingToConstructInterface(Telerik.Microsoft.Practices.ObjectBuilder2.IBuilderContext)
HResult : -2146233079
Stack Trace :    at Telerik.Microsoft.Practices.ObjectBuilder2.DynamicMethodConstructorStrategy.ThrowForAttemptingToConstructInterface(IBuilderContext context)
  at BuildUp_Telerik.Sitefinity.Web.UrlEvaluation.IUrlEvaluator(IBuilderContext )
  at Telerik.Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp(IBuilderContext context)
  at Telerik.Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp(IBuilderContext context)
  at Telerik.Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, Object existing, String name, IEnumerable`1 resolverOverrides)

Hello Anthony,

Please try to reinstall the Forums module by setting in the SystemConfig.config file for the Forums line:

In addition, please check the code in case you have any customization of the Forums widget and/or any other custom code related to the module, for example events handling in the global.asax.
Do you have the same issue with the default Forums widget on a page with build-in page template or without any template?

Regards,
Svetoslav Manchev
Telerik