Using the attached QML file and declarativevideo test application, it is possible to carry out the following test:
1) Press move to start video moving
2) Press pause to pause video
3) Enable task switcher (or activate keylock)
4) Select declarative_video test app (or unactivate keylock)
5) Press play to play video

Approximately 50% of the time the video is not shown when you resume playback by using the "play" button at step (5). The video window appears black (or partially transparent), although the audio starts corrrectly. The video remains undisplayed until the movement of the QML video item is stopped, when it will eventually restart.