Well, I went back and deactivated the Smush.it plugin and my site loaded fine, so it seems to be a problem with Smush.it.
My page is still getting a score of 100/100 with Smush.it deactivated, but it would seem I will have to activate Smush.it whenever I add an image to my image library in order to retain the benefits of the plugin.
Obviously, this is not how the plugin was designed to work and will be time intensive compared to having it running in the background.
I have posted to the Smush-it Wordpress.org support forum. Hopefully they will be of some help. If anyone here has any suggestions, I'd be happy to hear them. In the meantime, I am still very pleased with W3 Total Cache and love the GTMetrix.com Wordpress Optimization Guide. :)
