if you are using your operating system to adjust your operating system drivers to adjust your speed/ acceleration...TURN OFF enhance pointer precision(for gaming)
if you want to know why
"The ratio from your hand movement to you cursor movement must always be the same regardless of the speed you move your hand. Well that's if you want consistent accuracy. Enhanced precision basically makes it so the faster you move, the faster the cursor accelerates. It's best to keep this accel speed constant no matter how fast you move the mouse." so long story short keep it off.
if you are using your mouse drivers(logitech etc) turn mouse acceleration down to 0 also
