There's a switch that is screwed into the bottom of the brake master cylinder that sometimes goes bad and I believe it has something to do with shutting the cruise off. I had mine leak brake fluid and it will mess the connector once the brake fluid gets on there. I once had a condition where I couldn't get my cruise to come on and at the end of figuring it out and fixing it, it was my brake switch. Weird thing was that all my brake lights worked when the pedal was depressed, it just wouldn't allow the cruise to work. Your brake light switch could be bad, but I doubt it. Check the switch at the bottom of the master cylinder. There's also a brake on/off switch somewhere around the brake pedal I just don't know exactly where.