vsftpd does not allow local logins

On my fresh install of Ubuntu 12.04 64bit Server Edition I installed vsftpd using apt-get. I then edited the vsftpd configuration so that it has these options, and everything else commented out.

listen=YES
anonymous_enable=NO
local_enable=YES
write_enable=YES
dirmessage_enable=YES
use_localtime=YES
xferlog_enable=YES
connect_from_port_20=YES
chroot_local_user=YES
chroot_list_enable=YES
chroot_list_file=/etc/vsftpd.chroot_list
secure_chroot_dir=/var/run/vsftpd/empty
pam_service_name=vsftpd
rsa_cert_file=/etc/ssl/private/vsftpd.pem

When trying to login using a valid username and password I get the error "530 Incorrect Login"

the following errors appear in /var/log/auth.log

vsftpd: PAM unable to dlopen(pam_shells.so): /lib/security/pam_shells.so: cannot open shared object file: No such file or directory
vsftpd: PAM adding faulty module: pam_shells.so
vsftpd: pam_unix(vsftpd:auth): check pass; user unknown
vsftpd: pam_unix(vsftpd:auth): authentication failure; logname= uid=0 euid=0 tty=ftp ruser=<userid> rhost=127.0.0.1
vsftpd: pam_winbind(vsftpd:auth): getting password (0x00000388)
vsftpd: pam_winbind(vsftpd:auth): pam_get_item returned a password

The same exact settings worked on my 12.04 32 bit Server Edition. What might be wrong?