2004 SAAB 9-3 repair Question Traction Control failure lite

Twice in the last month while driving this lite came on and the car totally died while going 40-50 mph. Very dangerous as brakes, steering and all electronics are effected. Once we pull off the road and restart the car all is well. A mechanic checked it and said the computer check says it was the "traction control lite system and we would need to take it to a dealer for repair. It seems odd to me the whole car would shut down on a traction issue? Any info you can supply on how big a repair this is and how costly would be helpful. Also about two monhts ago we had to have a timing belt replaced, I don't know if this is at all related. Thank you.