Some more input for you:
When i start with CPU cables in, the PSU immediatley shuts off, doing a 'click' sound.
Just the mainboard PWR button shows and i can't start again.
I first have to turn off the PSU wait some seconds turn it back on again,
then i can try to boot again, with the same result.
I also tried another port on the PSU no difference.
I tried it with just one of the CPU cables, then i swaped the port on the mobo.
The only new thing to the setup is that i changed the RAM, but even with the old DIMM's no boot.