Solved mine. Two things went wrong. First was a noob error. I inserted the P4 4pins cable instead of the other 4pin cable (with two black wires) in the mobo. That solved made the cpu fan spin correctly with all psu cables attached. Second, I removed the mobo from case and it worked, seemed that a screw or something was shortwiring something when inserted in case. Now I reinserted the mobo in the case (only used 3 screws instead of 9, don't know if this is a problem ?) and everything seems to work.