LinqDataSource, select new { ... } = "The state information is invalid for this page and might be corrupted."

I had to temporarily delete the RadAjaxManager that was hiding the underlying error:

 TypeLoadException: Could not load type 'System.Data.Entity.DynamicProxies.RepricingApproval_40D472CCAE59DB7A70B40FC6B029B430955A5ED87A7670652AA5B4D9D96A9A38' from assembly 'EntityFrameworkDynamicProxies.Data, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.]