Sam;
We ran into this problem with an air-tool manufactureer, in Cleveland. We wound up installing a special shielded transformer, re-pulled every circuit on the computer network, 208/120, 3-phase oversized the neutral in all cases had a special panelboard made just for the problem and even installed insulated/isolated gronding receptacles. And for all our trouble we eliminated about 95% of the problem. Which was a huge improvement.
It is true to correct a problem like this it is costly and with DC/AC drives there is a similar problem but different order harmonics.
However I have never seen this problem in a residence.
