Microwave Sparking and several outlets not working
Sounds like the receptacles are just wearing out, and the spring contacts have gone weak so that they don't grip the pin properly. If your microwave is sparking at the socket, this would tend to reinforce this idea. 

If the receptacle contacts are not gripping the pin properly, there is a chance they will arc when current is drawn (as you have seen). Replacing the receptacles is the only way forward, I would think. All of them, even the ones which are still working.