Quote Originally Posted by lakedaemon View Post
I bought the motherboard on ebay...
Beside I'm french and I don't think asus sells WS Z7S in france...

So I guess that I have no warranty, or do I ?

note to self : don't buy motherboard on ebay...
I don't think your issue is with the board.
Where you commented on the loose power connector and if you wiggled it the system would stut down.
First, do not play with electrical connectors when powered except to read with a meter.
If loose, shut down and fix.
It is possible you damaged the board when you were moving that connector.
I would pull the cpu's, see if you damaged a contact pin in the socket.
Clear the cmos
See if you can get another PSU to borrow, at least 550w and a good quality one.
Make sure your memory is in the proper slots and seated well.
Check every connection to make sure it is properly done.
Sometimes the smallest errors produce the biggest problems.
Do each change one at a time and then try the system.
Good Luck