In App Purchase request results in password prompt

With In App purchase on IOS 4 when performing a product request or 开发者_Python百科SKPaymentQueue addTransactionObserver this results in the password prompt being shown. This occurs using a test user account. Why would this happen?

 productsRequest= [[SKProductsRequest alloc] initWithProductIdentifiers:productIdentifiers];
 productsRequest.delegate = self;

[productsRequest start];