> I have used a new subject line. If you see any problem that makes

  Changing the subject line is not enough. If you are reading another
email sent to the list, and you press "reply" or something similar, the
email you send will contain instructions to link it to the earlier
email, and many mailers will display them as one thread (see attached
image that shows how it is displayed in my mailer).  I suspect that's
what you've done here.  Technically, the problem is that your email's
headers contain a field "References", which they shouldn't; but from a
usage point of view the easiest is to simply start a new thread by using
the "compose" feature of your mailer, or equivalent.  As I see that
you're using Thunderbird, I'm surprised that it doesn't display the
emails in one thread, by the way.

	Arthur