Cannot Edit a Silverlight Viewer application

[ShawnyEkadis]

Using ArcGIS Viewer for Silverlight I was able to successfully create a web app but I cannot edit it. When I click on the icon to edit the map the Application Builder opens blank. If I click on the Home button I get an error message:

Unhandled Error [Arg_NullReferenceException]
Arguements:
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version4.0.60831.0&File=mscorlib.dll&Key=Arg_NullRefer....

If I click save then I get:

Unhandled Error [Arg_NullGeneric]
Arguements:
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version4.0.60831.0&File=mscorlib.dll&Key=ArgumentNull_....
Parameter name: map

So the only way out is to close the Builder. I thought this was supposed to be easy??

[Naeemuddin]

I have silverlight installed on my machine. when i am adding measureTool.Addins.xap or GoToCoordinates.AddIns.xap files downloaded from Arcgis.com it is showing the error "[Arg_NullReferenceException]
Arguments:
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=5.0.10411.00&File=mscorlib.dll&Key=Arg_NullRef...". I think it is the same error experienced by other users.

i am new to this domain and don't have programming background. Please advice how to resolved this issue.