Usually when a game just resets after start up or during gameplay once or twice its the silver 5 volt reg.

After u reseat all cables everywhere, and if it still does restarts and weird stuff, email Beaky about replacing the 5 volt reg, get a price to have it replaced, very very easy fix and not that expensive to do at all....one of the first things i do to alot of my machines if they ever do exactly what you have mentioned....