Probably Ive found the problem. Ive found some test programs which show errors constantly: prime95, hci-memtest, OverClock Checking Tool.
I got out all hw components except cpu, mobo, 1 memory module and booted from portable win7 usb-key. Did the tests and i didnt get arrors. I put in hws step-by-step and tested. I didnt get error until last step i put in the other memory module. then I tested both moduls in all slots one produced errors in all slots, other didnt produce error. So one of my memory modul was the problem.
Interestengly when I tested it with memtest86+ it didnt show error during 12 hours.
Now I tested only the bad nodule and finally memtest86+ shows errors too, but after a lot of time.
hci-memtest good module:
Attachment 292173
hci-memtest bad module:
Attachment 292172

So prime95, occt and hci-memtest show the errors maximum after 2 minutes, while memtest86+ needs a lot of hour.

I will mark this post as solved.

Bye K.