if you are not using the event afterRowActivate.. this will help

 private void ultraGrid1_AfterRowActivate(object sender, EventArgs e)

        {

            ultraGrid1.ActiveRow = null;

            ultraGrid1.Selected.Rows.Clear();

            ultraGrid1.AfterRowActivate -=new EventHandler(ultraGrid1_AfterRowActivate);

        }

it will remove selection and activation the first time, then the event is removed

hope this helps