I am running mysql server version 5.0.24 on debian sarge. I have a
table that was created as follows:

create table articles(id int(11) unsigned not null auto_increment,
title varchar(255) not null default '', body text not null default '',
date int(11) unsigned not null default 0, primary key (id),
fulltext(title,body));

I then inserted a row of data with the following query:

insert into articles values (NULL, 'this is an article about
penguins', 'The number of penguin species has been and still is a
matter of debate. The numbers of penguin species listed in the
literature vary between 16 and 19 species. Some sources consider the
White-Flippered Penguin a separate Eudyptula species, although today
it is generally considered a subspecies of the Little Penguin (e.g.
Williams, 1995; Davis & Renner, 2003). Similarly, it is still unclear
whether the Royal Penguin is merely a colour morph of the Macaroni
penguin. Also possibly eligible to be treated as a separate species is
the Northern population of Rockhopper penguins (Davis & Renner, 2003).
Although all penguin species are native to the southern hemisphere,
they are not, contrary to popular belief, found only in cold climates,
such as Antarctica. In fact, only a few species of penguin actually
live so far south. Three species live in the tropics; one lives as far
north as the Galápagos Islands (the Galápagos Penguin) and will
occasionally cross the equator while feeding.', 0);

When i run a fulltext search, such as the following:

select match(title,body) against ('penguin') from articles;

I get zero relevance for the article, even though it mentions the word
penuin several times:

+---------------------------------------+
| match(title,body) against ('penguin') |
+---------------------------------------+
|                                     0 |
+---------------------------------------+


Here are the fulltext-related variables i get from "show variables":

+--------------------------+----------------+
| Variable_name            | Value          |
+--------------------------+----------------+
| ft_boolean_syntax        | + -><()~*:""&| |
| ft_max_word_len          | 84             |
| ft_min_word_len          | 4              |
| ft_query_expansion_limit | 20             |
| ft_stopword_file         | (built-in)     |
+--------------------------+----------------+


Anyone have any idea what might be causing this strange behavior? I
have another server using the same versions of mysql and debian, and
it works fine.

Is this the only row in the table? You don't get fulltext matches
until you have at least 3 rows, because any word that matches 50% or
more of the rows is ignored as noise.