CNN have a 777 captain's take on what may have happened. Interesting (and entirely innocent) explanation of the repeated mention by the FO to Malaysian ATC of FL350, that it may have been a gentle nudge that they'd requested a higher FL in their flight plan and they wanted a further climb. I've heard this type of nudge many times as US-bound aircraft climb out from Heathrow towards the Welsh coast and get levelled off below their desired initial cruising altitude. Overall the article is another one inclined to a fire/malfunction scenario.
Opinion: How mechanical problem could have downed Flight 370 - CNN.com
[ I see the url has just been posted above ]