Many people have trouble implementing security in Access correctly.  The security FAQ available from Microsoft has not been updated since version 2000.  Although there isn't much that has changed, folks still seem to have trouble following the steps outlined.

Here are step by step instructions for Access 97/2000, and Access 2002/2003

Other good information:

Security Whitepaper from Microsoft
MSDN Library
MVP Lynn Trapp's
Jack MacDonald's

No Login Prompt - If you want to secure a database, but you don't want users to have to login.

Splitting a Secure Database - Don't use the database splitter wizard.

No permissions on MSysTables error
RWOP Queries
Remove security on a database
-Disabling the Shiftkey - Tool to enable/disable the shiftkey securely
Security Documenter

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