I've got a P55 with AIX 5.3 running with winbind successfully bound to
our Active Directory (Windows 2003 Server) environment, and the AIX
box is successfully processing authentications through AD when users
log in via "telnet" (yuck).

I've installed OpenSSH and that is successfully processing logins for
local users, but when I attempt to log in as an AD user, it
immediately logs the user out:
~]# ssh aix53sys -l myuser
myuser@aix53sys's password:
Connection to aix53sys closed by remote host.
Connection to aix53sys closed.

When I run /usr/sbin/sshd -ddd and I try to ssh in using an AD user, I
get (trimmed):
debug3: AIX/setauthdb set registry 'WINBIND'
debug3: aix_restoreauthdb: restoring old registry ''
debug1: monitor_child_preauth: myuser has been authenticated by
privileged process
debug3: mm_get_keystate: Waiting for new keys
debug3: mm_request_receive_expect entering: type 24
debug3: mm_request_receive entering
debug3: mm_newkeys_from_blob: 20080108(118)
debug2: mac_setup: found hmac-md5
debug3: mm_get_keystate: Waiting for second key
debug3: mm_newkeys_from_blob: 20080108(118)
debug2: mac_setup: found hmac-md5
debug3: mm_get_keystate: Getting compression state
debug3: mm_get_keystate: Getting Network I/O buffers
debug3: mm_share_sync: Share sync
debug3: mm_share_sync: Share sync end
debug1: audit event euid 0 user myuser event 2 (SSH_authsuccess)
debug2: User child is on pid 381052
debug3: mm_request_receive entering
debug3: AIX/setauthdb set registry 'WINBIND'
debug1: do_cleanup
debug1: audit event euid 0 user myuser event 12 (SSH_connabndn)

And I am seeing logged via syslog (which I hadn't noticed until I
started composing this message.. it has some interesting errors - I
re-
generated the keys to get the same result here, though.. I suspect
this is a red herring):
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug3:
recv_rexec_state: entering fd = 5
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug3:
ssh_msg_recv entering
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug3:
recv_rexec_state: done
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug2:
parse_server_config: config rexec len 163
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug3:
rexec:21 setting Protocol 2
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug3:
rexec:110 setting Subsystem sftp\t/usr/sbin/sftp-server
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug1:
sshd version OpenSSH_4.7p1
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug3: Not
a RSA1 key file /etc/ssh/ssh_host_rsa_key.
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug1:
read PEM private key done: type RSA
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug1:
private host key: #0 type 1 RSA
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug3: Not
a RSA1 key file /etc/ssh/ssh_host_dsa_key.
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug1:
read PEM private key done: type DSA
Sep 4 20:44:46 aix53sys auth|security:debug sshd[381062]: debug1:
private host key: #1 type 2 DSA

I'm not sure what else to check or why it is failing on the AD users
only.. telnet and other clear protocols work (rlogin, rsh), but,
as expected, we can't use those in our production environment...

-Rich