one newsgroup behaving odd

[alans-computer.local]

I use Gnus for usenet and have had this problem for months where
all my newsgroups work except for alt.zines. Alt.zines is always
shown as having 0 new articles. If I select it and hit the space
bar it says 'How many articles from alt.zines (default 27381):'
If I type 10, 100, 10000, or 20000 I just get one article from 
10-Jun-07. If I go with the default, or even a figure slightly
less than the default, I see the articles I've been missing all
along. Any ideas anyone?