Problems with gpg-agent and ssh

[James Davis]

After a hard disk died, I recently moved from Debian Etch to Ubuntu
Hardy and I'm in the process of rebuilding my gnupg/gnupg-smartcard
environment. The card is working fine for encryption and decryption but
I'm having some problems getting gpg-agent to use the authentication key
for my SSH logins.

When I run ssh-add...

$ ssh-add -l
The agent has no identities

and gpg-agent's logs say

2008-10-14 11:45:42 gpg-agent[11743] ssh handler 0x8097fe0 for fd 9 started
2008-10-14 11:45:42 gpg-agent[11743] ssh request 1 is not supported
2008-10-14 11:45:42 gpg-agent[11743] ssh request handler for
request_identities (11) started
2008-10-14 11:45:42 gpg-agent[11743] new connection to SCdaemon
established (reusing)
2008-10-14 11:45:42 gpg-agent[11743] secret key file
`/home/jamesd/.gnupg/private-keys-v1.d/717BA1D51659FA28DDD049724211B955B012D778.key'
already exists
2008-10-14 11:45:42 gpg-agent[11743] error writing key: General error
2008-10-14 11:45:42 gpg-agent[11743] ssh request handler for
request_identities (11) ready
2008-10-14 11:45:42 gpg-agent[11743] ssh handler 0x8097fe0 for fd 9
terminated

Any ideas as to what's causing this problem?

Thanks,

James