Progress.gif on checkout not resolving

In testing, before activating SSL and before adding/enabling Secure Pages, checkout worked great.

After activating SSL and Secure pages, couldn't access checkout. Realizing it tied to the URL switch between http: and https:, found the SSL Single Directory fix and made the change at the hosting site; that resolved the access to the page issue, but the checkout progress.gif image isn't resolving. It appears like it's loading information for manual or cc checkout, depending on which is selected. When you first go to checkout, it defaults to manual and the progress bar never stops "loading." Switch to cc method, same thing. Switching back to manual, the bar finally resolves and provides manual payment information.

Switch back to cc method, however, and it still doesn't resolve.

I initially set this as "critical" because our previous host (iPower) was having server issues and we couldn't access the site reliably, and were about to "go-live" with a convention registration. We did an emergency migration to Media Temple, where the site loads wonderfully, but we need to get this last issue resolved...it's 48 hours into the site move and registration window now. :/

Thoughts...? (Anyone thoughts on switching to the dev version of Ubercart's latest module to resolve?) We're using ubercart 6.22, Secure Pages 6.x-1.8, Drupal 6.16...

References:
http://drupal.org/node/554868 -- ubercart, similar issue
http://drupal.org/node/360893 -- secure pages, SSL Single directory fix