It sounds as though the two different db connections are getting confused. The error is telling you that it can't find your users table in the globalmix db. This seems correct based on what you have posed here since the users are part of the registration setup and those tables are in the GlobalMix2 db.
Do you maintain two different connection files for the site? If so it seems that you have one referenced after the other and the db that are being used are getting mixed up. You need to ensure that the connection to GlobalMix2 is included just before any of the user related code. If the wrong include is being referenced you will receive an error like the one you mentioned.
Do you have a requirement to use both databases for this? It is not conventional to have more than a single db referenced in a site like this unless there is a specific need for it. What happens if you combine the db's?