To reproduce :

1. Bind RadScheduler to data base. http://www.telerik.com/help/winforms/scheduler-data-binding-data-binding-walkthrough.html 
2. Specify the  AppointmentMappingInfo.AllDay property to the column in your data base table.
3. When starting the application, the all day appointments are shown correctly. However, if you try to drag the all day appointment to a new time slot and save the changes to your data base, the AllDay property is not stored.

Workaround: before saving the changes ,update the DataBoundItem's AllDay property:

Private Sub AppointmentDropped(sender As Object, e As AppointmentMovedEventArgs)
    Me.RadScheduler1.DataSource.GetEventProvider().Update(e.Appointment, "AllDay")
    SaveScheduler()
End Sub