Some power supplies have a little switch on the back that allows you to toggle between
120V and 220V. Even though it says the power supply should change voltage automatically, might be worth checking...

Also, the slots the RAM are seated in sometimes makes a difference. If the motherboard has four RAM slots, the second and fourth slots are the ones you use first. The pair of REM should match. If you have RAM in all 4 slots, the RAM in the first and third slots should also match each other.

If that still doesn't work, try putting in each individual stick of RAM just by itself to see if one of the memory sticks has gone bad. Good luck!