When you installed ssh server on the n900, were you prompted to set a password for root?
apt-get purge openssh-server
apt-get install openssh-server
gh@brasov:~/.ssh$ ssh -vv root@192.168.0.13 OpenSSH_5.1p1 Debian-5, OpenSSL 0.9.8g 19 Oct 2007 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to 192.168.0.13 [192.168.0.13] port 22. debug1: Connection established. debug1: identity file /home/gh/.ssh/identity type -1 debug2: key_type_from_name: unknown key type '-----BEGIN' debug2: key_type_from_name: unknown key type '-----END' debug1: identity file /home/gh/.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/gh/.ssh/id_dsa type -1