Resolution:
To determine which repository instances are available, XML Authority looks for the tibcfg.txt configuration file.  Check to make sure this file exists within the top level of your WINNT profiles directory (your user directory within "Documents and Settings").  If tibcfg.txt does not exist, you will need to configure discovery using TIB/Repository Manager.

If the file does exist, this typically means that you have configured discovery of remote repositories.  The current version of XML Authority cannot detect remote repositories, and will be unable to detect local repositories if remote repositories are configured for discovery (via TIB/Repository manager).  If you are unable to see your local repository through XML Authority, use TIB/Repository manager to configure discovery of local repositories only.
  
Note: As a work-around for remote repository detection, you can map the network drive where the remote repository exists to your machine and then configure the repository for discovery as if it is a local repository.  

When attempting to connect to the TIB/Repository, no instance names are available for selection.Why doesn't XML Authority detect my repository instance?