FTP doesn't work for non local accounts

[Andrew Afliatunov]

Hello!
On my Linux Slackware-9.1 server I installed nss_ldap and pam_ldap in 
order to Windows Active Directory users could use pop, imap and ftp on 
the server, authenticating in AD.
Everything worked fine while accounts where in /etc/passwd, - users 
could authenticate for those services in AD.
But then I removed accounts from linux system. Now users can use pop, 
imap, but can not connect through ftp.
proftpd.log says:
--
... no such user '<user>'
--
Why ftp doesn't see users in ldap, when pop, imap do? Maybe something 
wrong in the next files?
My nsswitch.conf contains:
--
passwd:         files ldap
shadow:         files ldap
--
/etc/pam.d/ftp:
--
#%PAM-1.0
auth       required     /lib/security/pam_listfile.so item=user 
sense=deny file=/etc/ftpusers onerr=succeed
auth       required     /lib/security/pam_shells.so
auth       sufficient   /lib/security/pam_ldap.so
account    sufficient   /lib/security/pam_ldap.so
session    sufficient   /lib/security/pam_ldap.so
--
/etc/pam.d/imap:
--
#%PAM-1.0
auth       sufficient   /lib/security/pam_ldap.so
auth       required     /lib/security/pam_unix_auth.so try_first_pass
account    sufficient   /lib/security/pam_ldap.so
account    required     /lib/security/pam_unix_acct.so
--
--
Andrew.