I came up with this theory in an earlier post, but he's right--there are a lot of holes in it. First of all, opening of a gear door would light up the control panel like a Christmas tree, unless all the sensors were immediately destroyed in which case the loss of sensors would have occurred over California instead of Texas. Second, a gap the size of the wheel well in the base of the Shuttle would have burned up and ripped apart the orbiter a heck of a lot sooner.

I think it was just a break in the tiles that was unusually deep or in an unusually bad spot on the orbiter, resulting in a burnthrough that eventually softened enough aluminum to let a big chunk of the wing fall off. After that, aerodynamic pressure would have done the rest.