Aside from that, it can easily be OC'd BUT, the problem comes in once you restart.
What PSU do you have? what program are you overclocking with? Is there more than one overclocking program on your computer? Have you overclocked it before? How exactly are you overclocking, specific clock changes and voltages? And what do you mean when you say the problem comes in once you restart, restart what exactly?
Ah, thank you for providing me with more questions.
PSU - Meh, It's the default of Dell P360.
Program - NVidia nTune.
No, I don't have more than one overclocking program.
Yes, I overclocked it before, the same results.
Clock Changes - I tried testing it with an increase of 20 MHz, malfunctioned.
Restart - I restart my computer for various reasons.
So, I still don't know why it malfunctions if I overclock it with such a low value.
And I also still don't know why it only malfunctions after restart.
Well it could be caused by any number of problems. Take my card for example, the maximum I can overclock on the core clock is only 10mhz, the last card I had could be overclocked by a massive 180mhz with still some headroom on stock voltages. All cards out of the same series of cards overclock differently. Your psu could be the problem, a ready built system probably only has an adequate PSU installed for the components installed, over seven to eight years the PSU's quality will have degraded. It could be nTune causing the problems as it tries to apply the overclock when it starts when windows boots up, try msi afterburner. It's an old card itself and the overclocking capabilities you have read about it are probably from a few years ago, the quality of the GPU will degrade over time.
@daship, too bad you didn't answer my question about why it malfunctions only after restarting.
@darkoil, so there are cases in which you can only overclock for 10 MHz? Thank you for the help. ^_^
So it's possible that it can't handle an OC of 20 MHz that's why it still breaks, I didn't think of that...