Thank you for contacting us.
From the error message, you have provided, it seems that the issue is caused by something missing, or outdated in your development environment . In this relation, could you please check if you have installed:
- Visual Studio 2010 with SP1 (or higher) - download from here
- .NET Framework 4.0 - download from here
- Silverlight 5 Tools for Visual Studio 2010 SP1 - download from here
- WCF RIA Services - download from here.
- SQL Server 2008 Express
Also, if you already have all these installed, have you tried to run the demos on other machines?
All the best,
the Telerik team