I ran into one problem with thumbnail display, emailed the developer and received a response within a few hours with a suggestion where/what to look for. His suggestion led me to discover a feature of the RocketTheme template I was using that injected invalid height and width attribs into the img tags; once I tweaked the template's feature everything worked great. (thank you Jan for the speedy support!)
For those needing to remove the credits from the footer; just make a small donation to support the developer and keep this great product alive. For my need, this one worked better than some expensive commercial extensions.