If you have your mouse working with the live-cd you can copy over the XF86Config-4 file to your hd.
This is what I have for PS/2:

Section "ServerLayout"
Identifier "XFree86 Configured"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "PS/2 Mouse" "CorePointer"
# Serial Mouse not detected
# USB Mouse not detected
EndSection

Section "InputDevice"
Identifier "PS/2 Mouse" # Match this with InputDevice above
Driver "mouse"
Option "Protocol" "IMPS/2" # Try PS/2 if it doesn't work
Option "ZAxisMapping" "4 5"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "true"
Option "Emulate3Timeout" "70"
Option "SendCoreEvents" "true"
EndSection