i had that same problem a while back with slackware. exept mine was a hardware problem. My ps/2 mouse port was bad so i had my logitech mouse plugged in the usb port, which died on occasion, so i had to have a serial mouse for plan b.
Make sure you have the right mouse selected in your /etc/X11/XF86config file (dont forget to backup the file if you change it). If you have the right one selected, try setting it to a more generic driver, 3 button PS/2 mouse would be good. Just do that to see if the drivers bad. Im asuming it has a scroll wheel so disabling that might fix it. sorry I can't help much.
[edit]Oops, didnt' see it was usb. that changes things a bit. dont use the ps/2 driver. lol[/edit]