I don't know the PSU's model but I know it outputs 550 watts as far as I remember correctly.Could be issue with PSU. What PSU model do you have currently?
Also could be issue with GPU. Aggressive overclock shortens life of components. Your graphics card may have deteriorated because of this.
I closed wallpaper engine and right now it hasn't been crashing.You can find out PSU model name by reading label on PSU.
Any OC means additional stress to components and in prolonged use can cause deterioration.
Please list full specs of your pc before and after upgrade.
Did you reinstall windows after the upgrade? If you don't do that, various performance/stability issues can surface.