if it works, then it's the fix.
actually, the ps/2 driver for linux was originally developed for older mouses - the ones with two buttons and no wheel. it's one of the first mouse protocols that was developed. the imps/2 has better support for most of the mouses today, which have the wheel, three buttons, or a button built into the wheel, ect.
this is my mouse section in XF86Config-4:
Section "InputDevice"
Identifier "Mouse0"
Driver "mouse"
Option "Device" "/dev/mouse"
Option "Protocol" "IMPS/2"
Option "Emulate3Buttons" "off"
Option "ZAxisMapping" "4 5"
EndSection
the "Emulate3Buttons" was an option for mouses with two buttons, and pushing them both simultaneously emulated three, and the "ZAxisMapping" has something to do with the wheel.