That Lepa PSU are garbage, never should be used for mining!
The LEPA 1600w is a fine PSU, nothing wrong with it.
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story5&reid=283OP, you simply piulled too much power through that 12v pin. Don't go over ~70w on a molex or sata chain. Any modular PSU will melt a connector if you pull too much power through it.