MBP click broken

Something weird has happened to my MBP Core Duo 2006 model.

Pressing the click button below the trackpad no longer registers the "clicks" in OS X. Oddly, when I plug in a USB mouse the left mouse button doesn't work, yet the right click works fine. It's almost as if the click functionality in OS X has ceased to work.

Any suggestions?

 

You are a god send, thanks!


For others:

1. Resetting PRAM and NVRAM
2. Shut down the computer.
Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
Hold the keys down until the computer restarts and you hear the startup sound for the second time.
Release the keys.