ssh connection closed after successful authentication

Since today I have a problem on my root server that drives me mad. Usualy I
can log in via public key authentication with no problem. Now I get:

debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Trying private key: /home/eggert/.ssh/identity
debug1: Trying private key: /home/eggert/.ssh/id_rsa
debug1: Offering public key: /home/eggert/.ssh/id_dsa
debug1: Server accepts key: pkalg ssh-dss blen 434
debug1: read PEM private key done: type DSA
debug1: Authentication succeeded (publickey).
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: channel 0: free: client-session, nchannels 1
Connection to xxxx closed by remote host.
Connection to xxxx closed.

so all looks fine, until at the end. What's wrong? Is my box cracked? The
web services run fine, so far.