"FYI the gfci doesn't really check ground fault in the sense some people on here think. A gf I actually checks current leak." Do you have a link to some sort of documentation for this voodoo theory? If that were the case, any time one GFCI in your house tripped because of a current leak, they ALL would trip. If the difference between the current leaving and returning THROUGH the current transformer of the GFCI exceeds 5 mA, the solid-state circuitry opens the switching contacts and de-energizes the circuit. http://m.ecmweb.com/content/how-gfcis-work The GFCI measures the DIFFERENCE in current between the hot and neutral that goes THROUGH the current transformer in the breaker. It can not sense a current that does not go through the current transformer. The GFCI may not reset if the main breaker is not turned back on first, or the LINE side neutral wire is not connected to the neutral bar yet, but it won't sense current leakage on a different circuit. If that were the case, how far away will it sense this "other" leakage? 100 feet? Your neighbor's house? The leakage in all the power transmission lines? Try this experiment, take the line wires off your doorbell transformer, and just wrap them around the transformer instead of hooking them up, and tell me if the doorbell still work ;) Or take your fluke and try to test for current without putting the wire INSIDE the current transformer. It is more likely that you just got unlucky with the new breaker being bad after the first one gave out.

"Supposedly Canadian FPE panels were different from ours and are not (as) dangerous. I wouldn't trust it anyway, but that's me." I've said it before and I'll say it again. Canadian FPE panels & breakers were and still are the most popular brand in Canada. They are consistently recommended and installed by countless electricians here. Thay are NOT, I repeat... NOT, of the same design or manufacture as the US version. I have no idea why you wouldn't trust them.

first, the fact that you replaced an outlet that was on an apparently unknown circuit underscores the importance of mapping all of the circuits in your house and always testing hot and neutral before touching them. if it had been a faulty outlet and you killed the power to the wrong circuit, it would have not been pleasant when you tried to replace the outlet. the first thing that came to mind with your description is that the one functioning outlet is the last in the series and the wires on the "load" side (so to speak, even though it isn't GFCI) somehow disconnected or the outlet itself is bad. that means everything on the other side of it won't work. just a thought. please don't touch any wires where there is a remote possibility that they are live. always test first.

"Only the breaker would, if enough total current was passing." Well, sort of. Just to dispel any possible confusion: A GFI breaker implements two functions. The first is overcurrent protection. The breaker trips if the total current drawn from the circuit exceeds the breaker's rating. For branch circuits this is normally 15 or 20 amps. The more it exceeds the breaker's rating, the faster the breaker trips. The second is ground fault protection. The breaker trips if it detects that the current is asymmetrical across the power line. The amount of asymmetrical (ground fault) current that trips the GFI part of the breaker is MUCH lower than the current that trips the overcurrent part . (Confused yet?) To explain this second function: it's not 100% accurate to describe it this way, but it's easier (I hope) to understand if you think of the electricity as going out the hot side of the receptacle and coming back in the neutral side. The GFI monitors both of these. If the amount of current coming back is less than the amount going out, some of it must be "leaking" to ground. That leakage might be going through a person or animal, risking shock or electrocution. So when the GFI sees that, it instantly opens, shutting off the power. With most GFIs, an imbalance (fault current) of 5 milliamps (0.005 amps) is enough to cause a trip.