1995 LeSabre Cruise Control

My cruise works at first and then shuts down. At first it was only occasionally, but now it does it almost every trip. I had a GM dealer check it out and after three trips to the shop and five hours in the waiting room, all that the could come up with was a bad ground (which they supposedly fixed). I have replaced the vacuum servo, and just today replace the Electronic Control Module (computer) and it is still a problem. Do I keep replacing parts or is there an answer to this problem? Please Help!