Can't tweak anything about synaptics touchpad

[Matteo Riva <muradin@gmail.com>]

After the full-upgrade of my testing system (with kernel 2.6.30) I
can't do anything about my touchpad anymore, with the main problem
being that I can't disable it.
Neither synclient nor xinput have any effect on it, and if I try

  gsynaptics-init

I get

  GSynaptics couldn't initialize.
  You have to set 'SHMConfig' 'true' in xorg.conf or XFree86.conf to
use GSynaptics

relevant part of xorg.conf:

  Section "InputDevice"
  	Identifier  "Synaptics Touchpad"
  	Driver      "synaptics"
  	Option	    "SendCoreEvents" "true"
  	Option	    "Device" "/dev/psaux"
  	Option	    "Protocol" "auto-dev"
  	Option	    "HorizScrollDelta" "0"
  	Option	    "SHMConfig" "true"
  EndSection

Any suggestion on how to turn that thing off again?

Thanks