Delphi + Access Database with password

Hi Experts, I have a problem about a protected Access database.
I make a softwware that uses an access data base, when I create it, I don´t put a password of security, then in my soft, i made the connection string (ADO COnnection) using jet 4.0, and a blank password and everything runs OK, now I need to put some security to the data base, and I try to put password to it using the security tool of Access, using the two forms, firs just a password, and second creating users... When I opne the *.mdb asks me for a password and user, y fill it and I can use the databes correctly, but when I try to connect whith the ado connection, changing the user and password raises an exception (error):
"Can´t start the application, The Working Information Group is mising or the file is opnend excllusivily by other user"
well, my Database it´s closed and there´s a file *.mdw in the same path of my database...

Where is my error=? when I put security to the database in Access or in the connection in Delphi... please haw can I correct it?

Thanks