IDEA not always working in GNUPG

[Anonymous Remailer (austria)]

Hi,

I occasionally receive messages encrypted by older PGP versions that are
not being decrypted by GNUPG 1.4.7

[scrubbed] gpg filename
gpg: assuming IDEA encrypted data
Enter passphrase: [scrubbed]

gpg: [don't know]: invalid packet (ctb=67)
gpg: WARNING: message was not integrity protected
gpg: [don't know]: invalid packet (ctb=0a)


Here is the output of gpg --version:

[scrubbed] gpg --version
gpg (GnuPG) 1.4.7
Copyright (C) 2006 Free Software Foundation, Inc.
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions. See the file COPYING for details.

Home: ~/.gnupg
Supported algorithms:
Pubkey: RSA, RSA-E, RSA-S, ELG-E, DSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH
Hash: MD5, SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

Is this normal behaviour? I'm getting round by using PGP to decrypt IDEA
messages that gpg won't decrypt but gpg does work with some IDEA
messages so I can't figure whats wrong.