Since the very beginning I was suspecting some problem with threads which could explain what is going on. However you said the code you posted was a complete testbed so the only threads running are those related to QNetworkAccessManager. Or at least that should be the case. On the other hand we can see around 10 threads in your app. Where are they coming from? Are you sure there is no additional code involved? Are you linking with some external libraries or something like that? Where does qmyapp.h come from?