To reproduce:
- Bind the control to a list of the following objects:
 public class MyObj
{
    public MyEnum TestEnum { get; set; }

    public MyObj(MyEnum testEnum)
    {
        this.TestEnum = testEnum;
    }
}

public enum MyEnum : int
{
    Value1,
    Value2,
    Value3,
    Value4
}

- Change the value and move to the next entry.
- You will notice that the value of the previous entry is not changed.

Workaround:
void radDataEntry1_BindingCreating(object sender, Telerik.WinControls.UI.BindingCreatingEventArgs e)
{
    if (e.Control is RadDropDownList)
    {
        e.PropertyName = "SelectedValue";
    }
}