Thank you FZ,
You might have just found out the cause.
As looking into the my processor specifications, I found out that it works with 1600mhz frequency at maximum frequency for memory sticks. Oh good, I really think I have changed it in Bios when I built the PC to make the memories work at 2000mhz.
I'll be at home in some hours. Will try both the fix you have provided earlier and will also try to lower the frenquency to 1600mhz. Will run tests on Graphic Card after that and send you the report. I'll also try to find the logs you have mentioned.
Link:
ARK | Intel® Core™ i7-3820 Processor (10M Cache, up to 3.80 GHz)
| Memory Specifications | ||
| Max Memory Size (dependent on memory type) | 64 GB | |
| Memory Types | DDR3-1066/1333/1600 | |
| # of Memory Channels | 4 | |
| Max Memory Bandwidth | 51.2 GB/s | |
| ECC Memory Supported ‡
| No | |
