Mac has a point, most computers will draw around 400 to 500 watts of power while in use unless a super fast gaming rig with top end multiple graphics cards and power supply to match, even then a full 1000 watts is pushing the boundary a bit too far.

However as we in the UK do call them electric shower units as that is what they are intended to be used for, they are an on demand water heater, modern units can draw as much as 10 kilowatts, though the average will be around four to eight kilowatts units. That is here in the UK with our mains supply at 240 volts, a full 10 kilowatt unit will draw 41.6 amps, an 8 kilowatt will draw 33.3 amps, and so on. In countries where the supply voltage is 110 volts the current is over double that for 240 volts with nearly 100 amps for a 10 kilowatt unit. At those currents it only needs a slightly loose connection screw to overheat the connection to the point of fire breaking out.
Although a loose or poor connection will heat up and eventually cause fire in the supply to a computer, the instability of the computer due to the bad connection, will hopefully have prompted an early enough investigation to rectify it.
Having said that, there is still the chance of one of the higher current components in the computer power supply, could be a Friday afternoon lemon and burn out. The recent problems with electrolytic capacitors going pop due to the wrong electrolyte being used, could also be a cause of fire as once blown can become a short circuit.