I agree with the above. MemTest will sometimes not report errors during testing but the RAM fails when in real use. But generally, if it reports errors, then it typically is bad. But, I am concerned with the number of problems you are having. Bad PSU, bad drive, and now bad RAM? It is certainly possible you are that unlucky and you actually received 3 bad components. But I wonder if your first PSU did not cause some collateral damage when it failed. I am suspicious like brinks and hope the failed PSU did not take out your CPU and motherboard too.