How old is the WH? It sounds to me like you may have a short in the wires leading to the elements, causing the reset button to pop. If it is not that old, I would recommend contacting AO Smith for their personal trouble shooting advice. Also, I'm assuming when you replaced the elements, they were not clogged with sediment, as this also may cause the elements to overheat. If there was sediment in the tank, did you flush it out?