Can't login with SSH using keyfile

hi Folks,

when I had seted up my server I set up SSH the way that users can only login using a keyfile, also root can login. Root can login with keyfile without problems!

Now I want to login as a user that is created by Virtualmin. Using a keyfile dosent work. It I chance the sshd that users can log in only with a password, the user can login.

I use Putty on Windows 7. It tells me "Disconnected: No supported authentication methods available (server send: publickey)"

In /var/log/auth.log I find:

Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_key_allowed: waiting for MONITOR_ANS_KEYALLOWED [preauth]
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_request_receive_expect entering: type 22 [preauth]
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_request_receive entering [preauth]
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_request_receive entering
Feb 20 22:47:27 hetzner sshd[6983]: debug3: monitor_read: checking request 21
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_answer_keyallowed entering
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_answer_keyallowed: key_from_blob: 0x7f7bd92bf200
Feb 20 22:47:27 hetzner sshd[6983]: debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
Feb 20 22:47:27 hetzner sshd[6983]: debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
Feb 20 22:47:27 hetzner sshd[6983]: debug1: temporarily_use_uid: 1016/1009 (e=0/0)
Feb 20 22:47:27 hetzner sshd[6983]: debug2: key not found
Feb 20 22:47:27 hetzner sshd[6983]: debug1: temporarily_use_uid: 1016/1009 (e=0/0)
Feb 20 22:47:27 hetzner sshd[6983]: debug2: key not found
Feb 20 22:47:27 hetzner sshd[6983]: Failed publickey for oliver-arp.de from 77.8.220.186 port 2855 ssh2
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_answer_keyallowed: key 0x7f7bd92bf200 is not allowed
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_request_send entering: type 22
Feb 20 22:47:27 hetzner sshd[6983]: debug2: userauth_pubkey: authenticated 0 pkalg ssh-rsa [preauth]
Feb 20 22:47:27 hetzner sshd[6983]: Received disconnect from 77.8.220.186: 14: No supported authentication methods available [preauth]
Feb 20 22:47:27 hetzner sshd[6983]: debug1: do_cleanup [preauth]
Feb 20 22:47:27 hetzner sshd[6983]: debug1: monitor_read_log: child log fd closed
Feb 20 22:47:27 hetzner sshd[6983]: debug3: mm_request_receive entering
Feb 20 22:47:27 hetzner sshd[6983]: debug1: do_cleanup

I used differnt keys. One created by PuttyGen and copied to the server, one created on the server (ssh-keygen) and imported to Putty.

Always the same errror. ~/.ssh is chmod 700 ~/.ssh/authorized_keys2 is chmod 600

Any ideas?