I get the message above after installing Debian 7 although I thought I have been able to connect since.

Here are the messages:
rene@asus:~$ ssh -v root@173.0.55.170
OpenSSH_6.0p1 Debian-4, OpenSSL 1.0.1e 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 173.0.55.170 [173.0.55.170] port 22.
debug1: Connection established.
debug1: identity file /home/rene/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/rene/.ssh/id_rsa-cert type -1
debug1: identity file /home/rene/.ssh/id_dsa type -1
debug1: identity file /home/rene/.ssh/id_dsa-cert type -1
debug1: identity file /home/rene/.ssh/id_ecdsa type -1
debug1: identity file /home/rene/.ssh/id_ecdsa-cert type -1
ssh_exchange_identification: read: Connection reset by peer

And here is the /etc/ssh/ssh_config:
Host *
# ForwardAgent no
# ForwardX11 no
# ForwardX11Trusted yes
# RhostsRSAAuthentication no
# RSAAuthentication yes
# PasswordAuthentication yes
# HostbasedAuthentication no
# GSSAPIAuthentication no
# GSSAPIDelegateCredentials no
# GSSAPIKeyExchange no
# GSSAPITrustDNS no
# BatchMode no
# CheckHostIP yes
# AddressFamily any
# ConnectTimeout 0
# StrictHostKeyChecking ask
# IdentityFile ~/.ssh/identity
# IdentityFile ~/.ssh/id_rsa
# IdentityFile ~/.ssh/id_dsa
# Port 22
# Protocol 2,1
# Cipher 3des
# Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
# MACs hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-ripemd160
# EscapeChar ~
# Tunnel no
# TunnelDevice any:any
# PermitLocalCommand no
# VisualHostKey no
# ProxyCommand ssh -q -W %h:%p gateway.example.com
SendEnv LANG LC_*
HashKnownHosts yes
GSSAPIAuthentication yes
GSSAPIDelegateCredentials no

I have no idea what the problem could be, can anyone help?

Thank you for your help.

check your local and remote permissions. to see more read the links in my sig.

With the -vvv switch I had a complaint (which I did not record) about the key so I adjusted /etc/ssh/ssh_config as per your instructions (plus what was already uncommented):
Host *
ForwardAgent yes
ForwardX11 yes
ServerAliveInterval 30
TCPKeepAlive yes
SendEnv LANG LC_*
HashKnownHosts yes
GSSAPIAuthentication yes
GSSAPIDelegateCredentials no
ServerAliveCountMax 5

and I deleted the existing keys, then created a new one as per your instructions, however trying to copy it to the remote did not work as shown below:
rene@asus:~$ ssh-copy-id -vvv -i ~/.ssh/id_rsa.pub root@173.0.55.120 25
OpenSSH_6.0p1 Debian-4, OpenSSL 1.0.1e 11 Feb 2013
Pseudo-terminal will not be allocated because stdin is not a terminal.
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
ssh: Could not resolve hostname umask 077; test -d ~/.ssh || mkdir ~/.ssh ; cat >> ~/.ssh/authorized_keys && (test -x /sbin/restorec: Name or service not known

It is still all behond my ability, can you help?

PS I now have an unwanted rsa_pub on the remote.

Thank you.

you can remove unwanted rsa_pub manually, also you can transfer the id.rsa_pub manually as shown in my links. the copy-ssh-id is a script to perform the same task as you can perform manually as per my link instructions.