I don't know how many of you live close to the border, as I do. But everytime I cross the border and enter France, the Treo won't switch the network automatically even though it is set to do so. Any hint??
If it stays on your country's network, it could be due to overlap. The towers don't just stop working at the border, they can usually carry over. For example, you can still get US carriers' signals in Niagara Falls, ON since it's just across the border from NY.