Debugging code is always easier when the code is provided. Your code should look something like the following:
$users = mysql_query("SELECT * from MailList");
$count = mysql_num_rows($users);
print "We have $count members and we are growing";
Or, easier should be:
$count = mysql_query("SELECT count(*) from MailList");
print "We have $count members and we are growing";
If your code doesn't look like either of these, please provide your code so we can see.
-spp