Musicman has a good idea, I would suspect that the NASA and contractor engineers would be looking for any differences in the shuttle systems data available from telemetry prior to and after the external tank insulation debris even.
brityank, my first impression of the NASA sensor timeline graphics brought me to the same preliminary conclusion you did concerning damage to the "orange" wire bundle - the failure mode of ALL of the temperature sensors in that bundle failed offline, there were no temperature changes noted. I do not know the type of temperature sensors used, thermocouples, RTDs, thermistors, or likely a mix, but it does not matter in this instance - its clear in the data then that there was no heating of these particular sensors to the point of failure. Exactly how the sensor wiring failed is not so clear, but certainly open to various theories at this point. If the sensors are indeed routed as per the NASA graphic, any damage near the wing cove/wheel well area could have caused this, whether the damage was exteme heat due to a wing breach, or physical damage due to debris. If I had to guess at this point, I would go with the leading edge RCC damage you postulate, or maybe even a significant loss of tiles on the wheel well area leading to a breach.
Of course, the precursor to all of this were the first sensor anomolies, which were increases in temperature of the brake lines. This was well noted in one of Ron Dittemore's early press conferences (Feb. 3?): http://www.newsday.com/news/health/orl-ss-nasa-transcript020303,0,5690321.story?coll=ny-health-utility
Hopefully, we will get more detailed techncial data from NASA, I don't expect it from the news media!
By the way, there is an excellent 3D cutaway graphic of the orbiter's left wing at the Orlando Sentinel:
http://www.orlandosentinel.com/news/custom/space/orl-asec-ssphoto020803,0,7510410.graphic
NASA must go through every branch of the fault trees, must not assume anything, in order to find the root cause. That is the essence of a good root cause analysis. I trust these guys, they will do a good job. But hey, what can I say- in the end, it will be the foam.