Steps to reproduce:
1. Use the RadGridView Smart Tag to set its data source 
2. Press "Add Project DataSource"
3. Select "Object"
4. Drill down and select the class you created. (see below)
5. Select the New Data Source
6. Run the project 

Code to reproduce:

public class TestClass
{
public enum Month { January, Febuary, March, April, May, June, July, August, September, October, November, December }
public Month TestMonth {get; set;}
public String TestMessage {get; set;}
public TestClass(Month month, String message)
{
TestMonth = month; TestMessage = message; }
}

Workaround:
Use BindingList instead System.Windows.Forms.BindingSource.