My bet is the power strip is now bad, and not providing enough power to your machines. This causes the voltage to drop and resets are common when that happens.
When you plugged the single game in to test earlier, did you have all of your other machines off, or were there other devices on the same circuit?
Test it on a circuit with everything else turned off. If you don't know how things are wired in your house, turn off all the lights and appliances in the same room and possibly the adjacent rooms. If it still resets, then you prob need your power boards rebuilt.
If it is fine, then it is either the strip, or you have something new on the circuit you haven't thought about - fridge, a/c or big TV?
I had this issue when I moved all my machines into a room for a tournament. They all played sluggishly and shut off when I turned on a big screen TV. I ended up running extension cords from other circuits until I renovate the basement.