Problem Summary. Hot Corners previously worked to start the screen saver. At some point, they just stopped working.
Problem Cause. If the computer has been in and out of sleep mode, and also has been in and out of screen saver mode, this could be causing the problem. There could also be some program causing a problem or a glitch in the OS.
Problem Solution. Restart the computer and the Hot Corners should work again.
Skill Level Required to Implement Solution. User must know how to restart the computer.
* The above fixed has been documented to work on one computer.