Small, but irritating Fps drops (60->59)

computer:
w7
i7 @ 3500mzh
2x 5850 crossfire
8 gig ram
and so on....

this computer i have should have no problem running Diablo 3 on max, so thats not the problem.

i play whit Vertical sync because i "dislike" tearing. i play the game i constantly have 60fps.

but at some random times (undependent on whats happening on the screen)
my FPS drops (MSI after burner says 59 fps, 60 normally)
Ctrl+r FPS flickers from 59-60.

this doesn't seem like much but it does stutter when it happens.
its not micro-stuttering because thats now how micro-stuttering works. This does not happen in any other games.

any change i can get feedback on this? is this a known issue or do you need additional information of any kind.