Why does 'ssh' and 'scp' work to one and not another?

[joe at actionline.com]

.
I have previously responded to each previous suggestion and request for info
to try to find a solution to the subject problem, and I will continue to
do so.  There have been three subsequent replies to this issue and I will
now reply to each one separately, in order.

First, kitepilot last suggested the following, with replies below:
> (1) grep joe /etc/passwd -- and post the line
> (2) find /var/log -type f -exec grep -H joe "{}" \; -- and post the output
> (3) Look at line:
> Feb 10 18:18:16 localhost su: pam_unix(su:auth): authentication failure;
> logname= uid=500 euid=0 tty=pts/1 ruser=joe rhost=  user=root
> (4) From console in 73
> ssh -v localhost (on 73) -- and post the reply
> (5) Then from the other machine do:
> ssh -v <73> (on 73) -- and post that too

(1) $ fgrep joe passwd -- result:
joe:x:500:500:Joe:/home/joe:/bin/bash

(2) $ find /var/log -type f -exec grep -H joe "{}" \;
Due to the length of the result of this command, I have uploaded that result
at the following link: http://www.upquick.com/linux/temp/var.log.joe

(3) Look at line:
> Feb 10 18:18:16 localhost su: pam_unix(su:auth): authentication failure;
> logname= uid=500 euid=0 tty=pts/1 ruser=joe rhost=  user=root

I have looked at that line, but I don't know what to do about it.

(4) From console in 73
ssh -v localhost (on 73) -- and post the reply -- the result is below:

OpenSSH_5.3p1, OpenSSL 0.9.8l 5 Nov 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to localhost [127.0.0.1] port 22.
debug1: Connection established.
debug1: identity file /home/joe/.ssh/identity type -1
debug1: identity file /home/joe/.ssh/id_rsa type -1
debug1: identity file /home/joe/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'localhost' is known and matches the RSA host key.
debug1: Found key in /home/joe/.ssh/known_hosts:4
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue:
publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Trying private key: /home/joe/.ssh/identity
debug1: Trying private key: /home/joe/.ssh/id_rsa
debug1: Trying private key: /home/joe/.ssh/id_dsa
debug1: Next authentication method: keyboard-interactive
debug1: Authentications that can continue:
publickey,password,keyboard-interactive
debug1: Next authentication method: password
joe at localhost's password:

> (5) Then from the other machine do:
> ssh -v <73> -- and post that too

Since I did the first 'ssh -v' on computer #73, by "the other machine"
I assumed you meant to do the suggested command on machine #68. Here was
the result:

$ ssh -v <73>
bash: syntax error near unexpected token `73'

Sorry if I did not follow your last instruction correctly, kitepilot.
Responses to the other two suggestions/requests will follow shortly.