set the references to copy local for the following dll's
For my latest application I had followed the directives as I found them on some websites and only copied the last 3 dll's to the bin folder. Which made sense because you get errors on the silverlight pages. But when I tested the application I got 'not found' errors when trying to read data. The System.Componentmodel.DataAnnotations.dll needs to be there as well for the RIA services to work.