Do the space bar move down when you press it? Can you make it work if you press harder that normal on it?
There may be some foreing material stuck under it.
Carefully lift it out to remove the obstruction then place it back in place.
Did you spill any liquid on the keyboard? Does the space bar move normaly but don't work?
In this case, it can mean that your keyboard have become defective and need to be replaced.
Electro, August 2012
