Can you check what version of the Xomega.Framework.dll is being referenced in your AdventureWorks.Client.WPF project? What path to the dll do you see in the properties of the reference? System.Windows, Version=18.104.22.168 belongs to the Silverlight package,
which you don't seem to have installed on your PC.
If your project uses the Silverlight version of the framework, then can you remove this reference and add a reference to the Xomega.Framework.dll compiled for the .net 3.5?
Also, are you using the samples from the current release or the latest one checked in the source control?
Please let us know if this helps.