[Plugin: WordPress SEO by Yoast] Error that messes with post editor

First off I’m using Thesis. Second, this was never before an issue until the most recent WPSEO update.

When trying to add images to a post via wysiwyg widget, I get this error:

keywords[i].replace is not a function
http://www.whatsthebigidea.com/wp-content/plugins/wordpress-seo/js/wp-seo-metabox.js?ver=3.1
Line 255

Any ideas?

Thanks