I have developed an application with app-purchasing. My app uses IAP 0.3.1. It works on X7 and 700, but there are some problems with C7 and N8. How I understand the problems lies in IAP Client. Below is debug log in the "simulation" mode:

[Qt Message] loadInterface("com.nokia.qt.IAP") returned  0 
[Qt Message] --> IAPClientImpl::IAPClientImpl(QObject *) 
[Qt Message] --> IapTestMode::IapTestMode(const QString &, QObject *) 
[Qt Message] IapTestMode::readTestModeFile: test mode "simulation" 
[Qt Message] IapTestMode::handleTestModeLine: invalid handling  "purchase"  for product  "#testMode" 
[Qt Message] IapTestMode::handleTestModeLine: product  "default"  is handled as  "simulated_ok" 
[Qt Message] <-- IapTestMode::IapTestMode(const QString &, QObject *) 
[Qt Message] IAPClientImpl::IAPClientImpl(): trying to connect existing server 
[Qt Message] IAPClientImpl::handleSocketError(): error code  QLocalSocket::ServerNotFoundError 
[Qt Message] IAPClientImpl::IAPClientImpl(): starting engine 
[Qt Message] <-- IAPClientImpl::IAPClientImpl(QObject *) 
[Qt Message] IapClientFactory::doCreateIAPClient(): client creation failed 
[Qt Message] --> IAPClientImpl::~IAPClientImpl() 
[Qt Message] <-- IAPClientImpl::~IAPClientImpl()