Recently the Service Stability System light and low traction light comes on while driving on dry pavement at highway speeds. Also , Stability System Active light and low traction light comes on at same conditions. It usually happens between 50-60 MPH , sometimes with the cruise on. I had it in to the dealer twice , and they said they could not duplicate it or diagnose problem. Any comments would be welcome.

If those lights are coming on, then a code is stored in the computer and the dealer has to use the Tech II scanner to read the codes. Most likely it'* one or more of your wheel speed sensors that are located in your wheel hubs. Here'* one of many threads discussing this topic:

http://www.bonnevilleclub.com/forum/...ic.php?t=93831

And another thread.
http://www.bonnevilleclub.com/forum/...ic.php?t=94081