When opening the Archive Attender console or trying to pull up the Users section, you may get an error that says:
Error getting the list of containers: Unable to load container configuration data: System.InvalidOperationException
Followed by a large amount of .Net XML errors. This error means that one of your container configuration files has become corrupt. These files can be found in the Service\Users folder of your Archive Attender install folder. Look for any files which are extremely small (less than a couple hundred bytes), and delete them or move them out of that folder.
The XML files contain the definitions for any user groups you have defined. When you delete the XML file for a group, users will be moved to the [Default] group on the next user scan. If the file you deleted contains the [Default] group definition, it will be recreated the next time you open the console.