I’m having this same issue.
This started after the plugin asked to do an Upgrade Databas, and actually nothing happened but corrupting the data.
No, it’s not a bad plugin.
In fact, it’s a very well done plugin, in which the developer clearly spent a lot of time giving attention to every detail, specially the configuration dashboard.
It’s very useful, very easy, flexible, polished and works out of the box.
I’ve hacked and messed up with it a lot, and absolutely nothing happened to my database.
It’s stable and safe.
This plugin is really good, and just what I wanted, but it’s not working.
It just keeps loading, like the friend above has said.