There seems to be a problem with the code in the WebKit bridge. Sharing a QImage or a QPixmap works as expected on Mac OS X, Linux and Windows in Debug mode. However, on Windows in Release mode the code throws an exception in QtWebKit. As its nearly impossible to debug I build a small test system:
What you can observe is that the object is complete, the method is available, however, the call will end in an exception. My guess is that in Release mode parts of the code in the bridge are optimized away because the exact same method works as expected on other platforms (gcc, clang) and in Debug mode.