It could be the psu but let's try simple things first.
Try uninstalling your current video drivers and downloading the latest ones off of the website. (Do this anyways even if you have the latest drivers)
Run memory test and check for errors on your ram.
Try underclocking your gpu. Download a program like msi afterburner and turn down the core clock by like 20 to 30 mhz.
Let me know when you do these things.