WPMU Dev SEO SEOmoz plug-in gets API error and provides no stats

The SEO plug-in is installed on my single-site WordPress 3.2.1 installation with MySQL 5.0 back-end database. I've gone to the SEOmoz.org site, signed up for an account, and received an Access ID and secret key from their site for the Free API. I've copied and pasted those values into the SEO plug-in and saved them. It immediately comes back with:

Unable to retrieve data from the SEOmoz API. Error: .

The SEOmoz displays on individual posts/pages are blank as well.

The other features of the plug-in seem to work fine, but I'm having no luck with this one.