This worked great for me! Thank you!
It is important to note that the entire procedure was necessary to fix this problem, at least for my set up. I've been fighting with this for some months now, and although I have tried the first 3 steps (setting the Safari preferences)--and tried them unsuccessfully--I had not before seen the recommendation to remove items from the /Library/Internet Plug-ins/ folder. It did the trick for me.
Thank you, thank you, thank you!