Good fps but micro-freezing sometimes

Hello there,

i am not the only one because i already saw someone on a server who has the same problem, here is the problem :

I got a new pc, a good one (100 fps ingame, i5 + gtx 670). But sometimes in game, i get very low fps for maybe 0,3 seconde, like a µ-freez (when jumping to a marine in skulk, it's very confusing and i often die because of that).

I tried to lower to minimum my graphic options, but the problem is still there.
I tried to verify the files integrity, no problem.
My drivers are up to date.
I got some some errors in the console about cinematics but i don't know if it's linked.