[Cruz]

// Find out how many threads this user has started
  $startcount1 = $DB_site->query_first("Select COUNT(postuserid) AS starts from thread where forumid='3' AND postusername='$userinfo[username]' AND open!='10'");
  $startcount2 = $DB_site->query_first("Select COUNT(postuserid) AS starts2 from thread where forumid='16' AND postusername='$userinfo[username]' AND open!='10'");
  $startcount3 = $DB_site->query_first("Select COUNT(postuserid) AS starts3 from thread where forumid='14' AND postusername='$userinfo[username]' AND open!='10'");
  $starts=$startcount1[starts]+$startcount2[starts2]+$startcount3[starts3];
  // end Find threads

that will work
you were resetting the variable $startcount with every different select query.