Going back just a bit:
SupplierSam #8157
Onetrack. #8161
I think it is too soon to dismiss fire/smoke as the primary cause of this aircraft disappearance. Have a look at this link:
http://www.aaib.gov.uk/cms_resources...ection%201.pdf
This fire in a B777 MEC burnt for little more than 15 minutes but the damage is considerable. The P200 and P300 panels ( containing ELMS, the power managment and distribution centre) were badly damaged and there was fire damage to the actual aircraft structure and wiring. During the incident, flight instrument displays were disrupted and there were no EICAS Warning or Caution aurals tones. Boeings opinion was that if this had occured in the air the crew could have received fire warnings for both engines.
Note that there is no smoke detection in the MEC that is visible to the flightcrew on EICAS, just a EQUIP COOLING OVBD advisory. There is no MEC fire detection or suppression.
There were similar incidents prior to, and after, this one. The cause was molten metal at up to 1000 deg C being released from BTB and GB contactors. The reasons why this happens is still not fully understood.
An airborne failure of this kind could have left the crew with an unmanageable situation due to multiple systems failure: VHF disabled, ACARS fail, dual FMS failure, flightdeck smoke, alternate nav diversion, loss of situational awareness, oxygen depletion, unconciousness, a/c nav to incorrect lat/long entry....