For some reason small movments of the mouse have no effect. This makes precise aiming very difficult and frustrating ( considering the god like accuracy of the enemy). I have tried all combinations of sensitivity and response bars in the menu. Any ideas? BTW running win 7 and i have a logitech G500 mouse.

Thanks for the post! I managed to solve the problem. It was the acceleration settings on the g500 software. I set it to a 1:1 ratio and that fixed it! Im a bit of an old school gamer i have never owned a fancy gaming mouse before. Well thats my exscuse anyway. cheers.