Mainly happens when I tried out Call of Juarez, Happened when I play Guild Wars in a zone I have never been in, and when I was playing World of Warcraft and Battlefield 2, happened quite a bit in there.
Full settings on anything and everything I play, until I get oblivion then I need to reel them down a tiny bit.
And now that I think about it it is more of a skip jump thing every few minutes, or if it gets bad max of about 30 seconds to a minute between each one, and they do go away after awhile.
However I have noticed that it mainly happens during online games, and when I do 3dmark05 or such there is no ski por jump during the 10 minuts it goes through graphics.
It is really quite bizarre, perhaps I never noticed it before because my computer was so crappy it was around 15 FPS on low during WoW =P.