In a post to another news group about wiring a 3-way switch leg with a
GFCI someone mentioned that the reason the GFCI was tripping when the
light was lit via the 3-ways is because the return current for the
lighting circuit returned to the panel via the neutral of another
circuit. The fix was to ungather the neutral for the lighting circuit
and direct it back through the appropriate neutral. OK. Fair enough.

But there was also some discussion of having to unbundle the bare wire
ground for the lighting circuit for the lighting circuit from the
second circuit also. I surely don't understand why.

As that thread has died out and I'm not getting any more information
about this and as I still need to complete that repair I thought I'd
ask here about the unbundling or ungathering of the bare neutral
wires. Why would it be necessary to have the ground wire grounded to
it's own circuit rather than through a second circuit. I've seen
bundled grounds all over the house even when there is more than one
circuit in the box.

Thanks

David