I had this identical issue with my Aspire 5600 notebook PC. I uninstalled the Synaptics driver and re-installed a new driver from the Synaptics site, re-booted only to encounter the touch pad still not operating. I happened to see this forum, used the FN +F7 key, and presto, back in business. Thanks for the heads up! You made my day!
6/1/12 at 8:35pm