Windows Phone: QNetworkAccessManager stops downloading after a random amount of time

The QNetworkAccessManager stops downloading after a random amount of time on Windows Phone 8.1. No signal (e.g. finished()) is emitted when the download stops. The problem occurs with different servers. The problem can also be reproduced when using a simple QTcpSocket for download.

The attached code can be used as follows to start a download:
WinrtDownloadTest* dl = new WinrtDownloadTest(this);
dl->download("http://ubuntu.lagis.at/releases/14.04.1/ubuntu-14.04.1-desktop-amd64.iso");

The app crashes (after a while) with the following output:
<code>
The thread 0xd00 has exited with code 0 (0x0).
The thread 0xd24 has exited with code 0 (0x0).
First-chance exception at 0x771D210B in winrtdownloadproblem.exe: Microsoft C++ exception: std::bad_alloc at memory location 0x05ABF290.
'winrtdownloadproblem.exe' (Win32): Loaded 'C:\Windows\system32\errorhandlingext.dll'. Cannot find or open the PDB file.
'winrtdownloadproblem.exe' (Win32): Loaded 'C:\Windows\system32\TDH.DLL'. Cannot find or open the PDB file.
Unhandled exception at 0x771D210B in winrtdownloadproblem.exe: Microsoft C++ exception: std::bad_alloc at memory location 0x05ABF290.
</code>