Did the whole thing -- un-rooted and S-On. The phone still random reboots.
Got to get another phone. 2 Arias available -- one rooted one not, both randomly reboot.
One other thought. After un-rooting, loading stock ATT rom, and re-rooting and loading CM7.2, I noticed when logging into Wifi at work that the phone had remembered multiple Wifi settings! Where is this info stored? It maybe a clue to something else to wipe and possible sole my rebooting problem.