I'm using an optical mouse on my laptop without a problem. Here's a copy of the relevant section of xf86Config-4 file:
Section "InputDevice"
Identifier "PS/2 Mouse"
Driver "mouse"
Option "Protocol" "ExplorerPS/2"
Option "ZaxisMapping" "4 5"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "true"
Option "Emulate3Timeout" "70"
Option "SendCoreEvents" "true"
EndSection

Does it help if you used this for your optical mouse? I changed the protocol to explorerps/2 because that would make the optical mouse work with the wheelmouse on 2.6 as well as 2.4.

HTH,

Durand