1. Logon directly to the database as the user that the quest application is trying to use
2. Try to do a select on syscat.tables
3. If that does not work, the user does not have access to the db2 catalog. Grant accordingly.
What is most likely happening is the user has access to specific non-catalog schemas but not the db2 catalog schema. Quest and other tools query the db2 catalog to build a list of tables on the system