The remote host is missing an update to openssh announced via advisory DSA 1576-2.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201576-2

Matt Zimmerman discovered that entries in ~/.ssh/authorized_keys with options (such as no-port-forwarding or forced commands) were ignored by the new ssh-vulnkey tool introduced in openssh 1:4.3p2-9etch1 (see DSA 1576-1). This could cause some compromised keys not to be listed in ssh-vulnkey's output. This update also adds more information to ssh-vulnkey's manual page. For the stable distribution (etch), this problem has been fixed in version 1:4.3p2-9etch2 We recommend that you upgrade your openssh (1:4.3p2-9etch2) package.