420A Instant power drain on key-turn

[$lacker]

2g NT Eclipse
Brand new battery (thought maybe the old one was the problem)
With a battery charger hooked up, everything works great
If I start it with the charger on, then remove the charger, it will continue working great
With the charger removed (but a fully charged battery), the headlights etc will work great, however the battery will drain instantly if I place the key in the "on" or "start" positions.
I might get a half turn out of the engine if I flip it quick.
Both the pos and neg battery cables show 0 resistance (great continuity) from the terminal to the destination, so I don't know what else it could be
Any clues?

It worked fine before, then I replaced the headlights, license plate lights, and power radio antenna. All of which work great, it appears, although this new problem has arisen

Thanks in advance

 

[96eclipzGsT]

Replace both battery terminals to start. The stock ones are painted black and cause problems.

 

[$lacker]

Just cut the old ones off the cables and re-use the cables?