What's wrong with the DC board?

I'm a hobbist who repair things just for the fun and the will to learn.

Recently, a friend of mine asked me to replace the shutter on his Canon EOS 5D Mark II, a kind of task I've performed before (with some help from a repair facility who adjusted the CMOS for me).

I can't find what I've done wrong so far: after I've reassembled the camera for a final check, I've found only the back LCD screen was backlighted, without any other sign of life. This kind of problem is well know: a blown fuse, the one numbered F601: http://www.magiclantern.fm/forum/index.p...

I had another working DC powerboard from a previous disassembly, and I've swapped with the one with blown out fuse, just for completing the final chech.

Well... after I've tried to turn the camera on... again, the same issue! The fuse blown immediately and the camera showed the same backlighted screen and no other sign of life.

Obviously, something is short-circuited out there, but I can't really find what. I've checked all the SMD components on all the boards, apparently they are all working.

Any ideas?