I didnt' post my files the first time I spoke here because I was SOOO happy that I was being able to play without the FPS drops (by deatcivating my antivirus/firewall and the in-game sounds) that I ended up playing lots of matches with a somewhat regular rate of 40-59 fps (but almost never reaching 60, either stoppig at 59 or sometimes going to 62 and dropping again). Those following matches have all been played with both antivirus/firewall and in-game sounds turned on like normal, and yes they did had several FPS "chokes" on several times during the matches.
I did send a ticket to chewbacca a couple months ago and he helped checking some stuff in my PC (up till the antivirus that I'm still waiting to do so I can get back to him...) and my old logs must be somewhere with you from that time, I decided to wait till I get money to buy a better PC to see if anything changes before answering him again (any day now... I hope). Anyway, here are my most recent logs and stuff, hope it helps somehow (I've always had those FPS drops since I know myself as a LoL player, but just recently they have become incredibly difficult to handle during teamfights, specially in Dominion).