Could be very frustrating. Once I had this intermittent memory board problem. Problem would surface every few months. Finally I decided to change it after realising the board was warped. warped memory board problem (ie the board is not flat) is quite common.
Once had to change a hard drive because my dog actually managed to flip my computer and it fell on its side. I almost changed the dog too, good thing I love him so much.
After trying out various suggestions from all of you, it turned out that one port of the surge protector ( with 8 ports, call it say SP-1 ) had grounding problem. I had plugged another surge protector ( Call it SP-2 ) into that port of SP-1 & had plugged 7 monitors & CPU into SP-2 which caused grounding problem in 7 monitors & Main chassis. I changed the port & it solved the problem. Still I called the electrician to check all wiring. He put in extra grounding in main supply & problem is gone. But I can't understand how grounding problem could give such a strong electric shock. I sincerely appreciate the suggestions from all of you & am very grateful.
I am glad that the problem was found, I know frustrating it can be to be in a similar situation. I still recommend monitoring the computer's temperatures and voltage from time to time as a precaution measure.
It takes at least two problems for this to happen. 1. Disconnected or Poor Ground. Chassis, frames, housings, etc. are grounded in the event that they ever become electrified with 'hot' or 'high' voltage, a short circuit will be created direct to ground. A problem arises when there is a disconnect (or poor connection) between the item to be protected, and ground. 2. The Chassis or Protected Item Becomes Electrified. If a hot, bare conductor contacts the chassis, and problem #1 above exists, then the chassis becomes electrified as if it were an extension of the conductor. Someone touching the chassis, and a grounded item, can be shocked. That person, in effect, completes the circuit to ground.