Query Help

I'm looking for a little query help, if anyone has a free moment...

I have two tables:

CREATE TABLE message_board_topics (
rec_num integer NOT NULL PRIMARY KEY,
topic_name varchar(255),
topic_body text,
topic_author varchar(20),
topic_author_email varchar(50),
topic_date date,
topic_updated datetime,
number_of_comments integer
);

CREATE TABLE message_board_comments (
rec_num integer NOT NULL PRIMARY KEY,
topic_id integer REFERENCES message_board_topics,
comment_parent integer,
comment_name varchar(255),
comment_body text,
comment_author varchar(20),
comment_author_email varchar(50),
comment_date date
);

Anyway, I want to do a quick and dirty search against them... Basically I
want to find any message_board_topic where the submitted text matches either
the topic_name, topic_body, topic_author, or the comment_author of any
related comment...

I tried this:

SELECT * FROM message_board_topics, message_board_comments WHERE
upper(topic_name) LIKE upper('%test%') OR upper(topic_body) LIKE
upper('%test%') OR upper(topic_author) LIKE upper('%test%') OR
(upper(message_board_comments.comment_author) LIKE upper('%test%') AND
message_board_comments.topic_id = message_board_topics.rec_num) ORDER BY
message_board_topics.rec_num DESC;

Now, this returns no rows but this query that doesn't search the comments
table returns a row:

SELECT * FROM message_board_topics WHERE upper(topic_name) LIKE
upper('%test%') OR upper(topic_body) LIKE upper('%test%') OR
upper(topic_author) LIKE upper('%test%') ORDER BY
message_board_topics.rec_num DESC;

Any ideas what I am doing wrong? It would be a big help.

Thanks,
Hunter