Periodic Massive Framerate Drop / GPU Usage non existent

[vijatoffee]

Basically, when playing games, this may also happen as a normal thing whilst browsing and youtubing etc. But i've been getting this extreme lag for some time now. Basically I looked at my EVGA Precision and screenshotted here http://i39.tinypic.com/207noso.png you can see that my GPU usage drops dramatically from anywhere around 90% down to 3% for around 10-15 seconds, then goes back to normal, and this is where I see the framerate lag, it drops to around 20% of its normal, regardless of what game i'm playing, This happens periodically around every 45 seconds or so, Could this be a power issue? Any suggestions on what I could do / test is greatly appreciated. The card i'm using is a Palit GTS 250 1GB, 4GB DDR2 Ram, 450W OEM PSU.

 

[vijatoffee]

Also my CPU is a AMD Phenom II 940 x4 BE (Neither CPU or GPU are overclocked).