Graphics card overheating upon computer boot up

Hello members of Tom's Hardware,
Less than a month ago bought a pre-built PC with a GT 630 graphics card, i7 3770 @3.4GHz processor and 6 GB ram. It served me well for about 2 weeks, but when I started it up I found that my games were stuttering and were running below the FPS they normally did. I then monitored the temperature on Speedfan: it was idling at 60-65 degrees celcius and the temperature would not drop; in fact, it would only increase if I opened a 3D application. So I tried rolling back to the previously installed display driver, and the temperatures suddenly went back to normal and the GPU was cooling down normally.

However, when I booted up my PC again the next day, the problem reappeared. I decided to update to the latest version of the display driver and the problem once again disappeared. I have no idea what the cause of this problem is, and dust is certainly not a factor. Is this a sign of a faulty GPU?

For reference, all my other temperatures are stable, even when the GPU is in its overheated state; CPU idles at 45 degrees, MOBO at 28 degrees and hard drive at 38. If someone could help me diagnose this problem at the very least, I would be grateful. Thanks in advance.