Just continuing with the weather theory, there have been some interesting posts on Flight International's site regarding AF flights and weather avoidance in the past.
Perhaps some of the long haul drivers may know whether on an ETOPS flight crews may be reluctant to go too far off course avoiding weather to stay within required ETOPS diversion times? Just a thought, if this crew did not in fact deviate around what looks like (from the satellite images posted) a pretty extensive belt of Wx.