//I changed the function from the following:  
    
    function _ad_channel_save_node($node) { 
      // delete old channel information, then add new 
      db_query('DELETE FROM {ad_channel_node} WHERE nid = %d', $node->nid); 
      $channels = _ad_channel_get_enabled($node); 
      foreach ($channels as $chid) { 
        db_query('INSERT INTO {ad_channel_node} (chid, nid) VALUES(%d, %d)', $chid, $node->nid); 
      } 
      if (user_access('configure ad premier status')) { 
        db_query('UPDATE {ad_priority} SET priority = %d WHERE aid = %d', isset($node->premiere) ? $node->premiere : 0, $node->nid); 
        if (!db_affected_rows()) { 
          db_query('INSERT INTO {ad_priority} (aid, priority) VALUES(%d, %d)', $node->nid, isset($node->premiere) ? $node->premiere : 0); 
        } 
      } 
        db_query('UPDATE {ad_channel_remnant} SET remnant = %d WHERE aid = %d', isset($node->remnant) ? $node->remnant : 0, $node->nid); 
        if (!db_affected_rows()) { 
          db_query('INSERT INTO {ad_channel_remnant} (aid, remnant) VALUES(%d, %d)', $node->nid, isset($node->remnant) ? $node->remnant : 0); 
        } 
    } 
 
//to the following : 
 
    function _ad_channel_save_node($node) { 
      // delete old channel information, then add new 
      db_query('DELETE FROM {ad_channel_node} WHERE nid = %d', $node->nid); 
      $channels = _ad_channel_get_enabled($node); 
      foreach ($channels as $chid) { 
        db_query('INSERT INTO {ad_channel_node} (chid, nid) VALUES(%d, %d)', $chid, $node->nid); 
      } 
      if (user_access('configure ad premier status')) { 
        db_query('UPDATE {ad_priority} SET priority = %d WHERE aid = %d', isset($node->premiere) ? $node->premiere : 0, $node->nid); 
        if (!db_affected_rows()) { 
     $isExists = FALSE; 
     $result = db_query('SELECT priority FROM {ad_priority} WHERE aid = %d',$node->nid); 
     if ($result){ 
     if (db_fetch_object($result)){ 
       $isExists = TRUE; 
     } 
     } 
     if (!$isExists){ 
     db_query('INSERT INTO {ad_priority} (aid, priority) VALUES(%d, %d)', $node->nid, isset($node->premiere) ? $node->premiere : 0); 
     } 
        } 
      } 
        db_query('UPDATE {ad_channel_remnant} SET remnant = %d WHERE aid = %d', isset($node->remnant) ? $node->remnant : 0, $node->nid); 
        if (!db_affected_rows()) { 
     $isExists = FALSE; 
     $result = db_query('SELECT remnant FROM {ad_channel_remnant} WHERE aid = %d',$node->nid); 
     if ($result){ 
     if (db_fetch_object($result)){ 
       $isExists = TRUE; 
     } 
     } 
     if (!$isExists){ 
           db_query('INSERT INTO {ad_channel_remnant} (aid, remnant) VALUES(%d, %d)', $node->nid, isset($node->remnant) ? $node->remnant : 0); 
     } 
        } 
    } 
  //If you are not already there. Here is the article on how to use this code http://www.actionscript-flash-guru.com/blog/50-warning-duplicate-entry-ad-module-advertisements-drupal-6.php