Night, did the mouse come with an optional USB port connector? Because on my borther's optical, the mouse acted psycho without being plugged into the USB. Also, on my friends, plugging it into the mouse socket made it work, but plugging it into the USB made it go insane. Don't know if that has anything to do with your problems, but thought it might be worth mentioning.
Also, Logitech has some really funky settings that may be causing the hyperactive sensitivity. One of the settings is Mouse Acceleration. I didn't notice it, but when my friend sat down to play some NS, he kept whipping about like a madman. After shooting everything on the screen but what he was trying to aim at, he made me look for the settings in the 'mouseware' taskbar helper and disable it.