symmetric encryption in a PGP-2 compatible way?

[svas@mail.ariadne-t.gr]

I attempted to conventionally encrypt a message in a PGP-2 compatible
way (usimg the idea extension), but it doesn't seem to work.

The file that gpg produces, with a command like:
	$ gpg  --symmetric --verbose --armor \
		--digest-algo=md5 --compress-algo 1 --cipher-algo=idea \
		--s2k-digest-algo md5 --s2k-cipher-algo idea --rfc1991 \
		--passphrase-fd=4 \
		MSG 4<PASS

seems to contain a packet of unknown length, as found with:
	$ gpg --list-packets --verbose \
		--digest-algo=md5 --compress-algo 1 --cipher-algo=idea \
		--passphrase-fd=4 \
		MSG.asc 4<PASS
	gpg: NOTE: THIS IS A DEVELOPMENT VERSION!
	gpg: It is only intended for test purposes and should NOT be
	gpg: used in a production environment or with production keys!
	Reading passphrase from file descriptor 4
	:encrypted data packet:
	        length: unknown
	gpg: IDEA encrypted data
	:literal data packet:
	        mode b, created 954292423, name="MSG",
	        raw data: 0 bytes

Then pgp2 fails to decrypt the produced file, while gpg succeeds in doing so.
Interestingly enough, pgp2 creates symmetrically encrypted messages
which are properly read by gpg:
	$ gpg --list-packets --verbose \
		--digest-algo=md5 --compress-algo 1 --cipher-algo=idea \
		--passphrase-fd=4 \
		MSG-generated-by-pgp2.asc 4<PASS
	gpg: NOTE: THIS IS A DEVELOPMENT VERSION!
	gpg: It is only intended for test purposes and should NOT be
	gpg: used in a production environment or with production keys!
	Reading passphrase from file descriptor 4
	gpg: armor header: Version: 2.6.3ia
	:encrypted data packet:
	        length: 86
	gpg: IDEA encrypted data
	:compressed packet: algo=1
	:literal data packet:
	        mode b, created 0, name="VER",
	        raw data: 67 bytes

It seems that the unknown length packet is giving pgp2 a hickup...
Is this a known bug or what ? After reading all the docs
I could lay my hands (actually my browser) on, I 'm still puzzled.
Any ideas ?  

Thanks in advance for any help,
- S


PS. This is gpg 1.0.1c running on a linux box
	gpg (GnuPG) 1.0.1c
	Copyright (C) 1999 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:
	Cipher: IDEA, 3DES, CAST5, BLOWFISH, TWOFISH
	Pubkey: RSA, RSA-E, RSA-S, ELG-E, DSA, ELG
	Hash: MD5, SHA1, RIPEMD160