LUALBA;
IF - I repeat IF - what the media has reported is true, I have the following remarks on your post:
To say that the TWAS failure is the primary cause of the accident is not true; if the pilots had selected the right flaps there wouldn't have been an accident - regardless of wether the TWAS was functioning or not. Please keep in mind that 99,99% (or there about) of all TO with the MD-80 are done without any TWAS warning and in most cases the pilots would not know if the system is working or not - because they've set the right configuration. I do agree that the absens of a TWAS warning might be a contributing factor in this becoming an accident.
Regarding GPWS and Stall they are designed so give warnings to the pilots in the air - not on ground (I don't know the MD-80 systems enough to know if the warnings are inhibited on ground or not).
The TWAS is configured to only give a warning when the plane is on ground, and thus a faulty ground/air switch in the nose gear (as has been suggested and explained in this thread elequantly) and the plane "belived" it was in the air the TWAS would be inhibited.
I would strongly recommend that you read through the thread - there is a bundle of accurate information from professionals to learn from.
Regards,
MjA