[AccessD] Connecting to SQL from Access w/a single login?

This is driving me nuts.  I know I did this a few years ago, but
right now I'm totally stumped.

A client of mine wrote himself an Access app for use around his
office.  Eventually the back-end swelled up to 500MB and problems
ensued, so they decided to go to SQL Server.  He upsized the database
himself and then called me in to help get the Access front-end
working against SQL Server.

Here's my current issue; I want all the Access clients to use the
same SQL Server login rather than having a unique SQL Server login
for each domain account.

I went ahead and created an AppUser login and gave it the appropriate
permissions to the application database.  I have the AppUser login
and password set in the ODBC DSN.  But whenever a user tries to
connect, an error message appears stating that his domain login was
not recognized by the SQL Server.  It's not even paying attention to
the AppUser info.

I'm surfing BOL right now, but haven't yet figured out what I missed.
And I know I'm missing something.

Any suggestions?
Respectfully,

Christopher Hawkins
Software Developer
(559) 687-7591
http://www.christopherhawkins.com