If somewhere in the electrical installation, someone swapped ground and neutral (it happens!) then you run into freak accidents where the appliance tries to pull current trough PE (protective earth) and that will give the issue that OP is having.
No, a reversal of live and nutral does not, and should not, affect a product with the CE marks in the E.U. That is because it is part to the safety standard.
Suddenly the ground connection on the external PSU is better than the one the PC has, and current will go that way - leading to hot wires.
No.