Steps to reproduce:
 1. Add two classes to the project:
public class ParentClass 
{ 
    public int MyProperty { get; set; }
    public List<ChildClass> Children { get; set; } 
}
public class ChildClass 
{ 
    public int MyProperty { get; set; }
    public SomeEnum Enumera { get; set; }
 } 
public enum SomeEnum { first, second, third } 

2. Add two RadGridViews to a form.
3. Add two binding sources one with DataSource the ParentClass, the second with DataSource the first binding source and DataMember "Children"
4. Bind the grids to the two data sources. 5. Edit some column properties of the grid bound to the second data source. 
6. Build the project and try to open the smart tag of the grid. Some times you will see a message box with text "Object does not match target type."