I've been aware of the various arguments from bottoming out with cold tires to the broken steering column. As I understand it there was a full racing lap before the accident so maybe the tires werent cold but then many drivers have at many times found it difficult to heat the tires. I think it must be some underlying mechanical issue there because when he veered off he didnt slow down at all.
Adrian Newey says this on the accident:
"If you look at the camera shots, especially from Michael Schumacher's following car, the car didn't understeer off the track. It oversteered which is not consistent with a steering column failure. The rear of the car stepped out and all the data suggests that happened. Ayrton then corrected that by going to 50% throttle which would be consistent with trying to reduce the rear stepping out and then, half-a-second later, he went hard on the brakes. The question then is why did the rear step out? The car bottomed much harder on that second lap which again appears to be unusual because the tyre pressure should have come up by then ? which leaves you expecting that the right rear tyre probably picked up a puncture from debris on the track. If I was pushed into picking out a single most likely cause that would be it."
If thats what he says then I would probably go for that since no one else would know that car better.