Probably lack of lube. Take it out and pull the inner cable out and clean it real well inside the sleeve and the cable. Then put a good coating of grease on it as you slide it back in the sleeve. If the cable is undamaged, it will be good as new.
Looks like it got too close to the exhaust, eh? When you put the new one on, make sure it is as far from the exhaust as you can! You can always put a spark plug insulating sock around the cable where it is nearest the exhaust, too. Something like this