OK, I found the line in the js and deleted it. The problem persists. What happens is that if I fill out a half-filled form (ignoring some of my added required fields), the "Required" message flashes on the screen for a second, then the email sends and I'm rerouted to the thank you page.
What would cause these javascripts to become corrupted? I'm not knowledgeable enough to have fiddled with them - I'm using them as-is from what DW provides. I sure would like to know where the errors are coming from.