Check this...
If you're speed sensor is off, it will stop your cruise from working. I havent checked the details of all of the other posts, they may have already told you to check this, but whek the speed sensor and the speed sensor gear. My friends cruise didnt work and his speedo was slightly chopy. We replaced the speedo sensor and the speedo gear on the end of the sensor that goes in to the tranny, and that fixed his cruise problem. Just an idea that may have been overlooked.
Aaron