[iSnow]

Unless there's a hardware fault, no runaway loop would overheat the system so much it would ignite.

[verelo]

Yeah you're probably right.

Often when you review critical failures you find multiple things went wrong at once to cause the catastrophic failure. I would place a good bet that there was a failed fan, poorly secured heatsink or maybe just a clogged air filter that meant the hardware was unable to handle the additional heat being produced.