The touchpad should have a the SHMConfig property set to "on". So it would look like:
Section "InputDevice"
Identifier "Synaptics Touchpad"
Driver "synaptics"
Option "SendCoreEvents" "true"
Option "Device" "/dev/psaux"
Option "Protocol" "auto-dev"
Option "SHMConfig" "on"
EndSection
That should help with disabling the touchpad. Also check if you have the synclient binary in your path.
Check your xorg.conf in /etc/X11/.
The touchpad should have a the SHMConfig property set to "on". So it would look like:
Section "InputDevice"
Identifier "Synaptics Touchpad"
Driver "synaptics"
Option "SendCoreEvents" "true"
Option "Device" "/dev/psaux"
Option "Protocol" "auto-dev"
Option "SHMConfig" "on"
EndSection
That should help with disabling the touchpad. Also check if you have the synclient binary in your path.