Ironclad: I too have a 8150 Ideos, i had trouble with mine roaming at Lake Hood near Ashburton, it roamed ok once out of Christchurch but lost service at Lake Hood and never regained it, i only realised something was wrong when we got back to Ashburton and still had no service.
It took a restart for it to work again, it has done it twice now once it has lost service it will not always regain it without a restart, it makes me not trust it when driving out of town you never know if it has regained service without looking at the phone.
Lake Hood is a notorious cellular blackspot - XT drops out not far from Lake Hood.