Thanks Monty! I think the issue was present whether hotlink protection was enabled or not. Perhaps it was related to .htaccess entries? Not sure. Regardless, the issue was resolved by detaching the site from Wordpress Toolkit (and no changes were made to .htaccess).
I have set up a few sites with a blog that feeds into a MailChimp RSS-based email campaign. This is a solution for pushing new blog posts out to an email list in a method that allows a good bit of control of the content and experience. Things were working great the first place I set this up. But...