I've been having this problem for some time now, anytime I play online the infected will start to jump around and sort of stutter while running. I've captured the problem in the video below as reference:
My system specs are the following: -Intel Core i5 750 (Quad core @2.6 GHz) -Nvidia GeForce 660TI -8 Gb RAM -Windows 7 OS
It doesn't seem to be my Antivius, my firewall or even my connection (my ping is a little low in the video but the same issue arises even when I or my friends host the game). Left 4 Dead 1+2 are the only games where i'm having this problem. TF2, UT2k4, CSS, HL2DM all work fine.
I'm asking for any help or thoughts someone may be able give.