This error indicates that the passphrase you entered is incorrect and that the private key file could not be read.
It also possible that the key file has been damaged, but this is unlikely.
This error will result in authentication failure (see section Authentication Failure) and disconnection (see section Disconnection). Click the OK button on both error dialogs to continue.
Try to connect again. If this error is repeated, upload your public key to the remote host computer again. For more information on this procedure, see section Generating a New Keypair.