MySQL simple replication problem: 'show master status' produces 'Empty set'?

Question

I've been setting up MySQL master replication (on Debian 6.0.1) following these instructions faithfully: http://www.neocodesoftware.com/replication/

I've got as far as:

mysql > show master status;

but this is unfortunately producing the following, rather than any useful output:

Empty set (0.00 sec)

The error log at /var/log/mysql.err is just an empty file, so that's not giving me any clues.

Any ideas?

This is what I have put in /etc/mysql/my.cnf on one server (amended appropriately for the other server):

server-id = 1
replicate-same-server-id = 0
auto-increment-increment = 2
auto-increment-offset = 1
master-host = 10.0.0.3
master-user = <myusername>
master-password = <mypass>
master-connect-retry = 60
replicate-do-db = fruit
log-bin = /var/log/mysql-replication.log
binlog-do-db = fruit

And I have set up users and can connect from MySQL on Server A to the database on Server B using the username/password/ipaddress above.