Hope I am not too late to respond. But, in the early days of computers, many manufacturers required separate "isolated" ground rods or fields. They wanted to eliminate noise on the lines so the sensitive computer equipment would not screw up the calculations. This meant that a fault, whether arcing or bolted, on the computer system would have to travel through the isolated ground, through the earth, then through the service ground system to get back to the main breaker for action. A low level arcing fault would unlikely not trigger the breaker to trip. I would check the isolated ground to make sure you are not getting some strange or stray voltage on it. This may mean renting some sensitive equipment from GE Supply or some other company. But it may find your culprit. Depending on the computer systems, you may now be able to tie the two ground systems together, and eliminate the problem. You will need to check with the manufacturer of the computers. Most newer computers of today don't require "isolated" grounds. Good luck.
