Shuttle Client in Adobe® Illustrator® doesn't remember the user specified in its Preferences. When you specify a user (i.e. an active directory user or Automation Engine user) in the Shuttle Preferences and launch Adobe® Illustrator®, it defaults back to the 'admin' user without password.
Symptoms
Every time you quit and restart Adobe® Illustrator®, Shuttle Client asks you to fill in the username and password. It doesn't seem to remember the Preferences filled in.
Solution
First of all, in case of active directory users, make sure these users were added on the server to the BGADMIN or BGUSERS group. To have enable an active directory user for Shuttle, you will need to login with that user at least once in the Pilot to make it 'active'.
Make sure that the user filled in the Shuttle Preferences is an existing user in the Automation Engine Server. If not, add this user to the BGADMIN or BGUSERS group or create a new user in the Automation Engine Pilot (Tools > Users). After creating the user, log in to the Pilot with this user once.
If you fill in a user that doesn't exist in the Automation Engine, then Shuttle will indeed default back to 'admin' next time you launch Adobe® Illustrator®.
For active directory users: Shuttle Client only remembers user name and password when using lowercase (e.g.,‘stef@esko’) instead of the uppercase (e.g.,‘Stef@Esko’), even though the user is listed as uppercase (e.g.,‘Stef’) in all user groups and the active directory.