Comment 5 for bug 180755

You should also have a section in the xorg.conf file that looks like this:
Section "ServerLayout"

 # Uncomment if you have a wacom tablet
 # InputDevice "stylus" "SendCoreEvents"
 # InputDevice "cursor" "SendCoreEvents"
 # InputDevice "eraser" "SendCoreEvents"
    Identifier "Default Layout"
    Screen "Default Screen" 0 0
    InputDevice "Generic Keyboard"
    InputDevice "Configured Mouse"
    InputDevice "Synaptics Touchpad" #the important line is obviously this one, add it to yours ServerLayout section if it's missing.
EndSection

Try issuing this command to see if the synaptics xorg module is loaded:
matteo@matteo-laptop:~$ cat /var/log/Xorg.0.log | grep synaptics
(II) LoadModule: "synaptics"
(II) Loading /usr/lib/xorg/modules/input//synaptics_drv.so
(II) Module synaptics: vendor="X.Org Foundation"

If it's loaded, try to install the gsynaptics package which provides an utility to configure the touchpad under system->preferences. Then try to enable the scrolling

Did you installed Hardy or you upgraded it from gutsy?