If you can get the cable moving again try some dri-slide http://www.amazon.com/Bike-Dri-Slide-4oz-Needle-Nozzle/dp/B001F2Y25G . Stuff works great. My trans cable was sticking and I tried a bunch of penetrating oils and cable lubes only to have it stick again after a few days. With the dri-slide I lube once a month and no problems since.

"Turbobitchero" (named by jealous wife) 87 swb base, 89 starion intercooled turbo engine, Bouncy seat, posi in rear, "miller locked" in the front with manual hubs, 3" BL, 305/70/16 bfg's. Sponsored by IAWDLR Racing