There is an interesting discussion thread here on The Aviation Herald which draws a rather speculative but, given a previous incident "Accident: Egyptair B772 at Cairo on Jul 29th 2011, cockpit fire" has some plausible points to consider.
http://www.avherald.com/h?article=44078aa7&opt=0Egypt Airs Boeing 777 was production number 71
Malaysian Airlines Boeing 777 was production number 404
Malaysian Airlines 777 was apparently NOT part of the batch of 282 Boeing 777s with the fault as identified as the cause of the Egypt Air cockpit fire.
The erratic flight path over Malaysian and Indonesian airspace and the POSSIBLE discovery of MH370 in the Indian Ocean?
To get there it would have had to turned left from its last known verifiable position, 02:15 last contact with military radar, which would also put it on a heading to the nearest airport in Northern Indonesia (was that the intention?) then, "If the wreck is found in southern Indian Ocean, draw a straight line from that point back to when the flight is known to have made its last turn and that's the point where something happened to incapacitate the crew, leaving the plane to continue on auto-pilot until fuel exhaustion."
Finally, if you subtract the distance spent meandering around in Malaysian and Indonesian airspace from the possible straight line fuel consumption range from Kuala Lumpur then the areas of POSSIBLE debris and pings are in the right range for fuel exhaustion. As commented in the thread earlier, if the on-board computer receives no further instructions after being instructed to head to the nearest alternative then it continues to fly that course until told to do otherwise or, fuel the runs out.
"To change course to an emergency airport all a 777 pilot has to do is go to the ALTN page of the FMC and select and execute DIVERT NOW. The aircraft will then turn and fly to the emergency airport, although it won't start a descent until a lower altitude is selected in the MCP."