Magic! New positive lead and ground to body and boom all is good!
Just to be clear here... You still did not replace the main negative cable to the engine block?
You do still seem to have fixed the issue and that's great. And more often than not it does turn out to be the short positive cable between the battery and starter relay, but if you did not replace the ground cable at the same time, then just remember that and if this ever happens again, start there.
If the current one is ok, then great. But they do wear out, and a bum negative cable could cause the same thing.
I'm curious now, why it always seem to be the positive side that has this happen to it. Maybe it has something to do with the fact that corrosion also seems to start at the positive side first? Just how the electrons flow I guess.
Paul