If you are actually still working on this problem, and it sounds like you are, I suggest this to start. Go back to the panel. Turn off EVERY breaker. Confirm that none of them are leaking with a Wiggy or a meter. Put away your plug tester and tick tester. Use a meter for accurate readings, because a difference of 10 volts or so can tell you a lot. Start testing for good voltages, and test the voltage from nuetral to ground every time, looking for anything more than 1-3 volts as a potential problem. Turn on one circuit at a time. That means turn off the others. If you see soemthing on one circuit not others, make sure that they are similar, ie. loads on or off. multiwire, etc. Then Look for multiwire circuits and turn them on as a unit and do the same. Remember what I said about a single electron running along the wire. If you find problems, I suggest you try to draw out the circuit from the utility in and trace the circuit (as one little electron) At this point, I personally would follow this to the end regardless of time, money loss. By this I mean, not that I would pay someone to do it, but I would spend my weekend there if I had to. Consider it school. You actually pay for that, and following this ot the end could teach you things you will never learn reading this forum or going to school.
I reiterate. Start from the beginning. Don't assume anything that you have already observed, such as 240 volts to ground was accurate. Confirm. Forst you NEED to determine if the problem is in the feeder or in a branch circuit. That will eliminate half your problem right there. One more thing. From a safety point anything you can do with resistnce instead of voltage is a good thing. Keep that in mind.
