Not a runaway stab, but this thread discusses an incident where FCS law reversion led to the autotrim function being stopped, leaving the stabiliser in the fully nose-up trim position. During the subsequent stall recovery the crew did not account for this and ran out of elevator authority as a result, losing control of the aircraft.
Definitely a reminder of how important pitch trim can be.
http://www.pprune.org/tech-log/52784...ml#post8160305