Hi Robert -- Given all the reports regarding bus mice recently, I was motivated to read the section on mice in the kernel-sources Documentation/devices.txt. (Should have done that a while ago.)
That indicates that if you have a Logitech bus mouse, you should either use Device "/dev/logibm" in your /etc/X11/XF86Config, OR use Device "/dev/mouse" if you've already executed: ln -s /dev/logibm /dev/mouse Good luck. Susan Kleinmann