ldapsearch password file format

How am I supposed to pass a password to ldapsearch using the -y <password file> option?
If I write the password in the password file in plain text, I get this error:

ldap_bind: Invalid credentials (49)
    additional info: 80090308: LdapErr: DSID-0C0903AA, comment: AcceptSecurityContext error, data 52e, v1772

The same happens if I use the -w <password> option.

EDIT:
The command I'm running is

ldapsearch -x -D <my dn> -y .pass.txt -h server.x.x -b "dc=x,dc=y" "cn=*"

Where the file .pass.txt contains my password, in plain text. Both the DN and the password are correct. If I run the command with the -W option and type the password on the prompt the command runs successfully, but I would like to store the password somehow to make a script.

Keep in mind that ldapsearch will use the entire contents of the file for the password--which means it WILL include a terminating newline character if one exists. To verify if this is in fact your problem, try creating a file without one:

echo -n ThisIsaBadPassword > .pass.txt

(UPDATE: Included '-n')

Assuming it is the newline/carriage reuturn try the following:

cat .pass.txt | tr -d '\n\r' > .pass2.txt

Then use the .pass2.txt file. You can always check for new lines and carriage returns with cat -vE and they will show up as $ and ^M respectively.

You could also probably do -y <(cat .pass.txt | tr -d '\n\r') directly in the ldapsearch command.