mysql_num_rows giver fejl

Hej

Jeg prøver på at banne folk i 5 minutter med følgende script:

Den giver dog fejl:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /var/www/domain.com/includes/banip.php on line 45
Error - Unable to insert records

Hvad gør jeg galt ??? :o)

På forhånd tak

<?php
$ip = $_SERVER['REMOTE_ADDR'];

$server = "localhost";
$table = "mail_ip";
$database = "db";
$username = "dbuser";
$password = "passwd";

$connection = mysql_connect($server,$dbuser,$passwd);
mysql_select_db($database,$connection);

$minutes = 5;
$seconds = $minutes*60;
$past = time()-$seconds;
$now = time();

if ( mysql_num_rows(mysql_query("SELECT * FROM $table WHERE ip=$ip")) != 0 ) {

mysql_query("UPDATE $table SET date=$now WHERE ip=$ip") or die ("Error - Unable to update visit");
} else {

mysql_query("INSERT INTO $table (id,date) VALUES ($ip,$now)") or die ("Error - Unable to insert records");

}
mysql_query("DELETE FROM $table WHERE date < $past") or die ("Error - Unable to delete old visits");
?>