When a user needs to read from an access table stored on a server (split database), a PC has to negotiate a connection to that server. If other users are using the database, then this can add a few seconds per table. If you have a database with say 10 tables, you might find that it can take 20-30seconds before a menu appears for a new user if the database is already in use.
To get around this we often add a hidden form or a hidden recordset connecting to a "dummy" table. This keeps the connection to the data database permanent or persistent, and the connection doesn't have to be negotiated each time. If the connections are being discarded by the server after a timeout period, this may also help with "network access interrupted" issue, although I am not sure about that.