How to diagnose tin being incredibly slow where other readers aren't?

I have just set up tin to read news from news.annexcafe.com.  I'm only
subscribed to six newsgroups there but for some reason tin is
completely unusable.

I have tin satisfactorily working with news.eternal-september.org
where I'm subscribed to far more (and busier) newsgroups.  Even when I
first used news.eternal-september.org it wasn't too slow building
indexes and starting up for the first time.

On news.annexcafe.com it's taking hours (literally, three or four
hours) to open a new group for the first time.  It then sort of works
but if I exit and then return all articles give "article unavailable".

Other newsreaders (I've tried pan and seaMonkey) work fine with
news.annexcafe.com.

What is the problem with tin?


-- 
Chris Green