OpenSSHアップグレード後にサーバーにSSHできません

私の開発者の一人が、OpenSSH 6.2pにバックアップせずに本番サーバーの1つを更新することに挑戦しました。このサーバーはEC2で実行されているubuntuボックスであり、SSHからの出力ログはここからSSHできませんコマンド。

ssh -i ~/Security/microsites_lamp.pem ubuntu@our.ip.address.here -v
OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
debug1: Reading configuration data /Users/justin/.ssh/config
debug1: Reading configuration data /etc/ssh_config
debug1: /etc/ssh_config line 20: Applying options for *
debug1: Connecting to our.ip.address.here [our.ip.address.here] port 22.
debug1: Connection established.
debug1: identity file /Users/justin/Security/microsites_lamp.pem type -1
debug1: identity file /Users/justin/Security/microsites_lamp.pem-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.7
debug1: match: OpenSSH_6.7 pat OpenSSH*
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-sha1-etm@openssh.com none
debug1: kex: client->server aes128-ctr hmac-sha1-etm@openssh.com none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<2048<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: Server host key: RSA <RSA_FINGERPRINT_HERE>
debug1: Host 'our.ip.address.here' is known and matches the RSA host key.
debug1: Found key in /Users/justin/.ssh/known_hosts:20
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /Users/justin/Security/microsites_lamp.pem
debug1: read PEM private key done: type RSA
debug1: Authentications that can continue: publickey
debug1: No more authentication methods to try.
Permission denied (publickey).

PEMファイルに適切な権限があり、サーバーが実行されていることを確認しましたが、今は動かなくなっています。何かできることはありますか？