and . . . . .
us Little Giant people want to know

can you get access to a Megger ? (high voltage resistance)

Oh the fault was not with the pump I think. The wires on the AC outlet were reversed (checked it yesterday). Glad I haven't plugged anything else of value into that outlet. Too bad it cost me a soldered up CPU though.

Basically, to get rid of EMI you need a very pourous metal such as nickel (commonly used to shield against EMI). You can buy EMI shield spray. It works fairly well at eliminating EMI completely. I think yahoo shopping has it. Anyway, because water is polar by nature, any magnetic fields that are generated by the pump will give water a charge which is what you're experiencing. You would have to coat the inside of the pump with the spray stuff as well, but then you may not have an operable pump.
The only thing I can think of is add a large concentration of a nonpolar liquid to your coolant...
-Zoson

That can't be the whole story though. For the miswiring to have an impact, there must have been a conductive path from the pump wiring to the CPU. (Magnetic field might be an issue as well, but the magnetic environment won't be changed by swapping the hot and neutral lines of the AC power.)

I think checking conductivity between the coolant and the wiring is still very important.