Originally Posted by
cyber3d
Since you car is still under warranty I say take it in for a diagnostic check. The cruise control is regulated by the EMS (CPU) and that EMS has a memory buffer that can help diagnose the problem and the source of the problem. In any case, be sure you take it in before you run the engine 40 times. At 40 times the buffer will be over written and you won't know the source of the problem.
Aside from using a GM diagnostic computer, there is not much beyond checking connections and the cruise button itself. The book recommends turning the steering lock to lock whilst cycling the buttons (the cables run along the steering column).
Goodluck