@Philwong
Did that and also with Windows integrated memory tester. Both were fine. But when i was running at same 1600MHz (doesn't matter which timing, be it 7-7-7-20 which worked fine or 9-9-9-24) it was always causing problems. Except when i bought the system. That's why i'm wondering what's failing at this point. Memory, motherboard or the CPU, considering it has memory controller integrated in it. But then again, if the memory controller or RAM was damaged in any way, wouldn't it be causing problems even at 1066MHz?