Highly doubtful. I think the explanations offered by NASA so far are reasonable: that security prior to launch was adequate to prevent any onboard sabotage, and that at the time of the accident, the shuttle was too high and traveling too fast to have been attacked from an external source.
If so, how, in your theory?
I have no personal "theory".
While I am just as interested in learning of the cause as is everybody else, I'm also resigned to the fact that a thorough investigation and analysis is going to take quite some time. I see no reason to engage in speculation or jump to premature conclusions.
Can someone explain to me if it would be possible to break into NASA's computer and cause the Columbia to re-entere at the wrong angle and burn in the atmosphere? The more explanations I hear on television, the more I wonder what are the chances that the first time NASA has lost astronauts on re-entry had to be when the israeli astronaut was on board!