It is still possible that there was a fire/explosion that only disintegrated the plane, although that is unlikely. That is, it is likely that the plane broke up mid air or as it hit the ocean.
This particular model of jet has a sort of “error correction” software, which can cause the aircraft to not perform as expected in very unlikely circumstances. I believe they have patched the bug (caused a couple of incidences of uncommanded descents)—http://www.flightglobal.com/articles/2009/02/18/322778/faa-mandates-third-a330-a340-inertial-navigation-fault.html
That said, it is possible that the radio comms were out when the electrical system fault began, and in the 4 minutes prior to the breakup of the craft (when the cabin pressure was reported to be lost by the automatic system), or they were busy trying to keep the plane up.