The pop-up was probably telling you that RD Tabs attempted to recover from a corruption and it used a recent automatic backup.If you go to %appdata%\Avian Waves\RD Tabs you will find all the settings files, which are quite different from 2.x. Settings, Favorites, and so on are in different files. There is a rolling automatic backup for each launch, you will see .history.1., .history.2., .history.3., etc. You can look at each one for well-formed XML and copy it over the "live" copy which is the one without the "history" part. You should be able to recovery a working copy from this data.The only things not backed up in this manner are scripts, but they are only overwritten at the time of editing.