The Times reports that the leading-edge flaw thesis just rose to leading theory, based on data recorder analysis:
Admiral Gehman also said today that the new data hinted that the shuttle already had severe damage when it began its re-entry, and not a minor flaw that was made worse by re-entry. Engineers had theorized that minor damage to the thin layer of protective silicon carbide on the panels could have allowed hot oxygen to begin eating away at the leading edge, but Admiral Gehman’s comments suggest that this is unlikely.
Damage before re-entry is likely, he said, because the data show extreme heating taking place early, while the force of air passing over the wing was still quite weak. Admiral Gehman spoke in a conference call with reporters this afternoon.
The damage referred to here as “severe” is also described as extant prior to re-entry. Does this implicate the mysterious shed matter, then? The article also notes that the foam debris shower could still be the cause of the damage.