The latest source code is not compatible with Visual Studio 2012.
According to the last link that was posted,
"You have to add a reference to Microsoft.VisualStudio.TestTools.UITest.Extension.Silverlight in your Coded UI Test Project. This assembly can be found in %Program Files%\Common Files\Microsoft Shared\VSTT\11.0\UITestExtensionPackages".
So basically you have to replace "Microsoft.VisualStudio.TestTools.UITesting.SilverlightControls" with "Microsoft.VisualStudio.TestTools.UITest.Extension.Silverlight".