The following is all speculation.
If they had a slat and/or flap misconfiguration that resulted in a too high AOA they could wind up in a deep stall, those T-tails are prone to. It is mostly unrecoverable even at high altitudes.
http://www.aviationtoday.com/regions/ca/3011.html
Lots of folklore about T-tail deep stall to find on the web. The FDR data should give an answer about that armchair hypothesis soon.