Fuel dump after regular flight?

I was a passenger in this uneventful 9h40m flight: http://flightaware.com/live/flight/CCA963/history/20120703/0600Z/ZBAA/EDDL

During approach, I could see the right fuel dump valve spraying for about 10 seconds (couldn’t see the left one).
Anyone got an idea why? Crew used the wrong switch by accident?

Perhaps over max landing weight and decided to dump than circle?

I doubt they were dumping fuel.

Sure it wasn’t just vapor trails from the flaps?

Like in this photo?

gallery.millerworks.net/Travel/P … 8w-M-1.jpg

I could clearly see that something was coming out from the fuel dump (jettison) valve:
I had taken this picture from my seat before the flight.

The incident took only a few seconds - the valve was only dripping a little bit when I had my camera out. But, it definitely looked like in this picture: http://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/FuelDumpA340-600.JPG/797px-FuelDumpA340-600.JPG.

On a side note, have a look at an Airbus overhead panel:
The fuel jettison buttons are placed the middle of the left panel.

Now compare to this (supposed to be from a 767-300):
contrailscience.com/skitch/Overh … 103650.jpg

Given Airbus’ rather inconspicuous fuel jettison buttons, could it be the pilot hitting these buttons by accident?

What happens in the cockpit when you do that, is there a warning?