What causes this ? Shift in cargo ?
I don't know Grieg, the reports I've read don't say. My first guess is that some of the machinery it was carrying has come loose in the rough weather. It would only only take one truck to break free, then as the ship rolls the loose truck (or whatever) gets flung about and more would come loose. With all the weight now sitting on what is now the low side the ship is would now be reasonably stable, and as long as the water doesn't get in, its probably unlikely to sink.
If water had got in, it would only take an inch or so of water across one of the vehicle decks to upset the vessel's stability, with the end result being what you have now.