Reseated a couple times, no solution.
I tried with another PSU ... same result. Arctic Cooling states that the PSU should meet the requirements. Have a look at my case and cooling strategy here:
http://www.arctic-cooling.com/pc_case2.php?idx=12.
20 Pin connector is well connected.
Getting out of options

. I guess I will try to rma the motherboard, and hope they don't mind that I replaced the Motherboard HSF with the Passive NB-47J Zalman cooler (hope that's not the reason the board malfunctions, guess not; anyway Asus should be ashamed of their stock NB HSF, such a freaking noise

). I can still put the stock version back on.
Thanx for your help.