QDrag Pixmap problems on Windows 7 (64Bit)

I have a problem with pixmaps in QDrag class. The problem is that directly after entering the QDrag::exec() function a "destroyed" image appears beneath the mouse cursor. "Destroyed" means there are black/white lines in the image. The image is on "hot-spot" position (0,0) even if there's another hot-spot set. This "destroyed" image appears only a very short time. Sometimes the whole screen flickers for a short time too (depends on the pixmap set with QDrag::setPixmap()). One time I got a destroyed mouse cursor. After that short strange behaviour the dragging is working correctly. I tested Qt 4.7.2 as well as 4.7.3 (all 32 bit) under Windows 7 (64 bit). The problem also appears in the Qt Drag&Drop Puzzle and the Drag&Drop DragableIcons example. The problem does not appear in the GraphicsView DragDropRobot example.

Thanks...