So if you haven't done so already, perhaps try my steps below.
However, in the end I managed to get it working again. So I also started to fear Hardware malfunction. I tried rebooting, removing the battery, blowing under the button (in case some dirt got lodged there). (An externally plugged in mouse, works fine though.) When I woke up my VAIO from sleep today, the left button and touchpad tap didn't seem to work any more. I'm using a vpc-f13z1e, and got it/started using it 7 days ago.
I've actually had the exact same thing happen to me just now.
