If the first user opens any form, report, macro or code, the database is locked exclusively to that user - from Access 2000 forward. Also in Access 2007 forward there is an option to open a database exclusively, and that can be set as the default for a user. Check those two possibilities out - for that reason, we usually give each user their own local copy of the queries, forms and reports in a split database structure where only the tables are in the shared database.