Thanks for the clarification pal. It seems to be a
driver(synaptics) issue.
Mind removing and downloading the latest
drivers and check..
Drivers | Synaptics
UPDATE: In my acer, eventhough I have the driver cd, I havent installed the synaptics thing. But still, I am able to use the touchpad while any key is depressed. Why not give it a shot. Remove the synaptics thing and then try.