Thanks for reply.
Yes, I checked that troubleshooting post before writing here thanks to google.
Rechecked everything, well except testing with one stick of memory, or changing slots. See, my system is taken apart already, was going to rma MB, but had doubts. Before building again, I was thinking to find some advice where to look for the problem. On Monday I will probably reassemble again, maybe with the help of "breadboarding" and see what it will tell me.