Not writting to database..Please help

I purchased this script in PHP and it's not writting to the database. Irf someone could have a look and tell me why I sure would appreciate it the code is :

PHP:

<?
include("common.php");
$link = mysql_connect($dbhost, $dbuser, $dbpassword)
or die("Could not connect: " . mysql_error());
  mysql_select_db($dbname);
  $sSQL="select n_ID, n_RefererID from t_Users where b_Activated<>1 and s_Username=\"".stripjunk($username)."\" and n_Rand=".stripjunk($rand);
  $results=mysql_query($sSQL);
  if(mysql_num_rows($results)==0)
  {
  include ("header.php");
   echo "Sorry, either you followed a broken link, the account specified is already active, or it doesn't exist";
    include ("footer.php");
  }
  else
  {
   list($n_ID, $n_RefererID)=mysql_fetch_row($results);
 $sSQL="update t_Users set b_Activated=1 where n_ID=$n_ID";
 mysql_query($sSQL);
 $sSQL="update t_Users set n_Credits=n_Credits+$referral_credits where n_ID=".stripjunk($n_RefererID);
 mysql_query($sSQL);
   include ("header.php");
 echo "Congratulations, your account is now active, please click <a href=./login.php>here</a> to log in";
    include ("footer.php");
  }
mysql_close();
?>