[XNEWS]Retain headers & articles?

I'm learning to drive Xnews and there are a couple of things I
haven't been able to figure out.

AFAIAA the version I"m using is the latest: 2006.08.24.

I would like to have Xnews save headers downloaded from a given
server so that this list only needs to be refreshed with the latest
new threads/posts next time I connect. Ideally I'd also like it to
save the articles I've read so that I can use the Custom Filter
function to search within the body of read posts.

To this end I've tried using the 'Storage Option' for each server;
I've set it to 'Store Headers and Articles'. Problem is that Xnews
does what I expect it to for some servers but not others.

Some examples...

news.mozilla.org -- When I subscribe to the
mozilla.support.thunderbird group on this server although a list of
threads and posts soon appears in the this group's window, every time
I fire up Xnews and open this group Xnews starts downloading the
entire list of threads/posts on the server for this group. This takes
a while to complete -- there's 40,000 of 'em. The same occurs with
subcriptions to all groups on this server.

The same thing happened when I setup access to the
terabyteunlimited.com newsgroup server (port 1198). Each time I
access groups on this server in Xnews it downloads the complete list
of headers instead of refresing it.

When I started out I with Xnews I was quickly able to make it retain
the headers and articles as I expected it to. The first server I
setup an account for was nntp.aioe.org. All of the groups I subcribe
to on this server retain the list of threads/posts; articles are
saved too. When I connect to subscribed newsgroups the list on
threads/posts in refreshed with the recent arrivals just as I want it
to be.

As far as I can tell, and I've checked repeatedly, the settings for
all servers and newsgroup subscriptions I've created are the same.
The Storage Options for each subscription is set to 'Store headers
and articles'. For each server I've tried hitting the Save Newsrc
button before exiting to no avail. Why are subscribed groups on some
servers behaving differntly to those on other servers in Xnews?

Previously I've used Thunderbird to access newsgroups. TB does not
have to reload the list threads/posts from scratch each time it
connects to a subscribed group.

I am aware of the 'Refresh Headers Special' function but don't want
to limit the topics available to search.

What might I do to have subscribed newsgroups retain headers and save
articles consistently?

Another strange behaviour that I cannot reverse has manifested with
the View | Show All Headers function. Initially Xnews was not
displaying full headers but I turned it on, I thought temporarily, to
view a couple of user agent strings. Despite trying to turn this
function off article views default to display full headers.

Help with these settings would be appreciated.

David
.