ISO10.6.8? Do you mean the Mac OS 10.6?
If this is a Mac system there are three possible issues. If this is windows, skip the first one.
1) On mac systems there is a utility called "keychain" that can enter account names and passwords for you when you open a fileMaker file. Sometimes a change is made to it or your computer's user account or you switch to a different computer and then you get a request for a password that you didn't get before.
I'm not a mac user, but others have discussed this one here in the forum.
2) In FileMaker's File Options every file is set to auto-enter data for the account name and password. The default setting is for the account name of "admin" and no password. For a newly created database file, this is the default account that is automatically created. As long as this account exists, and the option for auto-entering a password is selected in File Options, the file will open without asking for a password.
If you specify a password or change the name of the admin account in Manage | Security, you now get the password dialog. If you clear the check box for an auto-entered account name and password, you'll get a password dialog.
So if you get a password dialog, try Admin as the account name and leave the password box empty if you can't otherwise open the file with full access privileges. Once you get the file open, you can check File Options and Manage | Security to see what might be causing this.
3) Sometimes the request for a password is not for the file you initially opened. A reference to data or a script from another filemaker file can trigger a password dialog to appear for that additional file if there is no account name and password defined in that second file that exactly matches the account name and password used to open the first file.