Can you give us the details of the memtest86+ testing?
This could be a RAM settings issue, with some details we can take a look at them.
Can you download CPUZ
and post a snip of the CPU, Mainboard, Memory, and SPD tabs.
For posting the information , enter 'Snipping tool' in the Start button > Search box, hit enter. Select the area you want to post and save to a convenient place. How to Post a Screenshot in Seven Forums
Have you been checking your temperatures? Use Real Temp
, to check the CPU temps when at idle, under load and/or testing.
Let us know the minimum and maximum temps you get.
Go to your BIOS and tell us what the CPU, RAM and North Bridge (NB) voltages are.
This is very important, required to adjust the RAM settings.