[CentOS] usb mouse config

Hello.
I have 5.2 running nicely on my Aspire laptop. It has a 'mousepad' 
(which I don't like), so I put a usb mouse on it.

It works properly, but I (apparently) can't change the motion (in 
Preferences > Mouse, Motion tab). Any setting for the Acceleration and 
Sensitivity don't affect the motion.

Do I have to config something somewhere else?