hi,
Need more details on which state you are setting the values in page behind, is this Page:Load? if so try this
if(!IsPostBack){//SET YOUR RADIO BUTTON LIST DATA}
Another workaround is the way you are setting data, you should use
String myValue="MayBe";
rblTakeHoliday.SelectedIndex=
rblTakeHoliday.Items.IndexOf(rblTakeHoliday.Items.FindByValue(myValue));
Hope this will help.