decrypt : primary key or subkey ?

[Bruno Costacurta]

Hello,
I'm not able to decrpyt message as I received hereafter message about using 
subkey instead of primary key. 

Is this correct ? Could it be the problem relies on the usage of this subkey ?
If yes, how to manage my keyring regarding this 
subkey (which is obviously used for en/decrypting not for signing) to be able 
to decrypt ?

gpg -v -v --decrypt msg.asc
gpg: armor: BEGIN PGP MESSAGE
gpg: armor header: Version: GnuPG v1.4.6 (GNU/Linux)
:pubkey enc packet: version 3, algo 16, keyid 42531C9A0CC897B5
        data: [2048 bits]
        data: [2048 bits]
gpg: public key is 0CC897B5
:encrypted data packet:
        length: unknown
        mdc_method: 2
gpg: using subkey 0CC897B5 instead of primary key 2E604D51
gpg: encrypted with 2048-bit ELG-E key, ID 0CC897B5, created 2006-06-11
      "Bruno Costacurta <bruno at costacurta.org>"
gpg: decryption failed: secret key not available

Bye,
Bruno

-- 
PGP key ID: 0x2e604d51
Key : http://www.costacurta.org/keys/bruno_costacurta_pgp_key.html
Key fingerprint = 713F 7956 9441 7DEF 58ED  1951 7E07 569B 2E60 4D51
--
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