Problem decrypting a mail with an OpenPGP card

[Michael Bienia]

Hello,

I've got three mails (from the same person) with my signed key (one for
each uid). I can decrypt two of the three mails but not the third:

$ gpg broken-gpg.mail 
gpg: sending command `SCD PKDECRYPT' to agent failed: ec=6.131
gpg: encrypted with 1024-bit RSA key, ID AF58F2B4, created 2006-03-13
      "Michael Bienia <michael at vorlon.ping.de>"
gpg: public key decryption failed: general error
gpg: decryption failed: secret key not available

$ gpg2 broken-gpg.mail 
gpg: encrypted with 1024-bit RSA key, ID AF58F2B4, created 2006-03-13
      "Michael Bienia <michael at vorlon.ping.de>"
gpg: public key decryption failed: Conditions of use not satisfied
gpg: decryption failed: No secret key

gpg is version 1.4.6, gpg2 is version 2.0.4 and I'm running Ubuntu
feisty. I'm using the gpg-agent but I've also tried without the agent
but it failed also.

What could be the problem?

Here is the output for one of the working mails:

$ gpg2 -vv good-gpg.mail 
gpg: armor: BEGIN PGP MESSAGE
Version: GnuPG v1.4.6 (GNU/Linux)
:pubkey enc packet: version 3, algo 1, keyid FB50DDA4AF58F2B4
        data: [1024 bits]
gpg: armor header: 
gpg: public key is AF58F2B4
gpg: using subkey AF58F2B4 instead of primary key 968BD587
gpg: public key encrypted data: good DEK
:encrypted data packet:
        length: unknown
        mdc_method: 2
gpg: using subkey AF58F2B4 instead of primary key 968BD587
gpg: encrypted with 1024-bit RSA key, ID AF58F2B4, created 2006-03-13
      "Michael Bienia <michael at vorlon.ping.de>"
gpg: AES256 encrypted data
:compressed packet: algo=3
:literal data packet:
        mode b (62), created 1180971809, name="",
        raw data: unknown length
gpg: original file name=''
gpg: good-gpg.mail: unknown suffix

and here for the non-working mail:

$ gpg2 -vv broken-gpg.mail 
gpg: armor: BEGIN PGP MESSAGE
Version: GnuPG v1.4.6 (GNU/Linux)
:pubkey enc packet: version 3, algo 1, keyid FB50DDA4AF58F2B4
        data: [1013 bits]
gpg: armor header: 
gpg: public key is AF58F2B4
gpg: using subkey AF58F2B4 instead of primary key 968BD587
:encrypted data packet:
        length: unknown
        mdc_method: 2
gpg: using subkey AF58F2B4 instead of primary key 968BD587
gpg: encrypted with 1024-bit RSA key, ID AF58F2B4, created 2006-03-13
      "Michael Bienia <michael at vorlon.ping.de>"
gpg: public key decryption failed: Conditions of use not satisfied
gpg: decryption failed: No secret key


Michael