Truthfully, I wouldn't let it trouble you much man. I have an Athlon 1.0ghz, GeForce 3 Ti500 and I get 20fps with 8 or more people in the game. I have tried every driver, system setting, and even took-apart and rebuilt my computer. I just equate it to bugginess at this point. Don't let it trouble you. I just tend to stick with games of 8 or less.
However, I am running with everything at max (except complex shadows of course...too much strain on my gpu). Sorry couldn't be more of a help
