Possible ownership/permissions issue?

I have run an earlier version of Majordomo on one of my systems over 
the past 10 years or so, and had very little problem setting it up and 
getting it operating.

Recently, my main server crashed with a catastrophic hardware failure, 
and I am in the process of rebuilding my system and adding a backup 
system.

The machines are HP servers, running HP-UX 11.11 with all updates. I 
also installed gcc and other software needed by it,  and bash, pine, pico, 
Apache, etc. Sendmail is version 8.13.X

E-mail is working fine as is the web server.

I tried to set up Majordomo 1.94.5 according to the most recent 
documentation, but am having difficulty.

The setup is as follows:
userID: majordom
group: daemon
majordomo home directory: /opt/majordomo
permissions on $home: 0770
permissions IN /opt/majordomo/lists: 664

In the aliases file at /etc/aliases, I have setup the first alias as

majordom : majordomo

in addition to those listed in the majordomo.alias file.

I can mail to [email protected] from root or a local user 
and it works fine. I get the proper responses, etc.

However, when I attempt to mail to my [email protected], I 
receive several messages at the list manager as follows:

"The original message was received at Mon, 17 Aug 2009 22:09:02 -
0700 (PDT) from daemon@localhost

   ----- The following addresses had permanent fatal errors -----
:include:/opt/majordomo/lists/<list_name>
    (expanded from: <list-name>-list)

   ----- Transcript of session follows -----
550 5.2.4 :include:/opt/majordomo/lists/<list_name>... Cannot open
/opt/majordomo/lists/<list_name>: Group writable directory

    [ Part 2: "Delivery Status" ]

Reporting-MTA: dns; foo.somewhere.edu
Arrival-Date: Mon, 17 Aug 2009 22:09:02 -0700 (PDT)

Final-Recipient: RFC822; <list_name>[email protected]
X-Actual-Recipient: 
rfc822;/opt/majordomo/lists/<list_name>@foo.somewhere.edu
Action: failed
Status: 5.2.4
Last-Attempt-Date: Mon, 17 Aug 2009 22:09:02 -0700 (PDT)"

Will/can someone please tell me what the heck is going on?

What is this "Group writable directory" business? As far as I can see, the 
directory in question MUST be "group writable".

I am confused...which is not an unusual state for me. :-(

Kenneth G. Gordon
Electronic Instrument Specialist, Sr.
University of Idaho
College of Science
Moscow, Idaho 83844-3025