Cruise control Quits

When I set my cruise control all is fine untill the vehicle speeds up over the speed it is set for ( such as a 2 mile hill on open road) at this point the cruise stops working and will not reset untill the ignition is switched off and then restarted.I can drive all over town and it works fine untill I go down a long hill.Dealer says no code is there and im getting no help.pcm was reflashed when on a trip to the south ( no help ) Will be going in for 3ed time this week,any ideas?