Web Forms Trouble Safari

Safari was developing some loading issues, so I did a Time Machine reset of it recently. Since then, I can't use the TAB, ENTER, or DELETE keys while completing web forms. A few examples—I go to Wikipedia to look up something, type it in the search box, and hit ENTER. Safari then freezes up and I get a beach ball. Command-Option-Esc tells me that Safari Web Content is Not Responding. Another example, attempting to fill out a sweepstakes form—I put in my first name, then hit TAB to go to the last name field. As soon as I hit TAB, Safari freezes up and I get the beach ball. Or say I type my email address wrong in a "Contact Us" form. So I try to backspace with DELETE to fix it. As soon as I hit DELETE, Safari freezes up and there's a beach ball.

I'm running OS X Yosemite for those who will inevitably ask. Safari's problems before the Time Machine restore were completely different, and those have gone away. But what's it calling when I hit those keys in web forms that causes the whole program to hang?