I do not now if I have the same problem, but I found very simple solution for mine:
When I switch touchpad off with "Disable" button (physical button near touchpad) and reboot, my touchpad starts working again.
The problem reappear, if I reboot with the touchpad switched off again.
So it looks like either Gnome or Synaptics Driver dose not save ON/OFF state when you reboot, and another thing (Gnome or Synaptics Driver) does. And after reboot their ON/OFF states are inconsistent.
I do not now if I have the same problem, but I found very simple solution for mine:
When I switch touchpad off with "Disable" button (physical button near touchpad) and reboot, my touchpad starts working again.
The problem reappear, if I reboot with the touchpad switched off again.
So it looks like either Gnome or Synaptics Driver dose not save ON/OFF state when you reboot, and another thing (Gnome or Synaptics Driver) does. And after reboot their ON/OFF states are inconsistent.
I use Acer Aspire 5740 and Ubuntu 10.4.