Meg, I offer my condolences also. The machine should have been confiscated for a complete examination. Was this done?
If so, what was the outcome?
Was the machine connected with an extension cord.
Was the cast iron pipe examined to see if it could have possibily had voltage on it?
I know this is probably not something you want to go through again, but the more info you can give the more we could eliminate as to the possible cause. (to a point)
As Bren points out GFCI's do quit providing protection and still work under some conditions.
I have three in my house that stopped working as far as protection after a lightning hit, yet all still worked as far as power.
Roger
