@achmed88 A friend of mine has this problem too, but I think it might've been fixed for him. Try deleting your profile file in AppData/Local/Insurgency. You won't lose anything and it might fix the bug.
I think I fixed my Sandstorm performance issues. For some reason, setting Texture Streaming to High actually solved it.
I've had this same issue since the second Alpha, I was on the New World Interactive's live stream and the person running to suggested to randomize your appearance, yet that clearly does nothing. Still waiting for a solution.