Before trashing the effect, try reverting After Effects Preferences to their defaults by holding down the Control + Alt + Shift keys while launching the application. (Command + SHift + Option on the Mac).
Thanks for your advice Brian. I decided to try something else before I took your advice. I hate having to reset all of my preferences, and I always try to make that my last ditch effort.
I moved my Knoll Light Factory folder (HD/Library/Application Support/Adobe/Common/Plug-ins/CS5.5) to my desktop. Then I restarted AE and deleted the layer that had the Knoll Light Factory effect that was causing the trouble. Then I saved the project, restarted AE, and had no problems. Then I closed AE, returned the LF folder to the original folder and restarted AE.
And I'm good as gold. I figured I share my solution in case anyone else has the same problem.