I've had OpenSSH server running on my debian server for a couple weeks and all of a sudden now when I go to login the next day it rejects my ssh key and I have to manually add a new one each time.

Not only that but I have the "tunneling with clear-text passwords" option enabled and the non-root (login with root is disabled) account for that is rejected too.

I'm at a loss why this is happening and I can't find any ssh options that would explain it.

--update--

I just changed debug level to DEBUG. But before that I'm seeing a lot of the following in auth.log

Feb  1 04:23:01 greenpages CRON[7213]: pam_unix(cron:session): session opened for user root by (uid=0)
Feb  1 04:23:01 greenpages CRON[7213]: pam_unix(cron:session): session closed for user root
...
Feb  1 04:36:26 greenpages sshd[7217]: reverse mapping checking getaddrinfo for nat-pool-xx-xx-xx-xx.myinternet.net [xx.xx.xx.xx] failed - POSSIBLE BREAK-IN ATTEMPT!
...
Feb  1 04:37:31 greenpages sshd[7223]: Did not receive identification string from xx.xx.xx.xx
...

My sshd_conf file settings are:

# Package generated configuration file
# See the sshd(8) manpage for details

# What ports, IPs and protocols we listen for
Port xxx
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes

# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 768

# Logging
SyslogFacility AUTH
LogLevel DEBUG

# Authentication:
LoginGraceTime 120
PermitRootLogin no
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile     %h/.ssh/authorized_keys

# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes

# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Change to no to disable tunnelled clear text passwords
PasswordAuthentication yes

# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

X11Forwarding no
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no

#MaxStartups 10:30:60
#Banner /etc/issue.net

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

Subsystem sftp /usr/lib/openssh/sftp-server

UsePAM no

ClientAliveInterval 60

AllowUsers myuser