แจ้ง error มาแต่ไม่เข้าใจค่ะ ... Warning: require_once(DB.php) [function.require-once]: failed to open stream

<?php
// ที่เก็บไฟล์: /core/admin/index.php
session_start();
require_once("../../core/template_secure.php");
require_once("../../_library/_class/class.admin.php");

if(!session_is_registered("sAdmin"))
{
header("Location:../../site/advertise/");
exit;
}
if(isset($_GET["path"]))
   $path=$_GET["path"];

$oSess = new admin;
$aAdmins = $oSess->getAdmins("created_dt desc", $iCursor);
$iCnt = $oSess->getAdminsCount();
if (count($aAdmins)) {
    
    $i = 0;
    while ($i < count($aAdmins)) {
        $aData[$i]["Id"] = $aAdmins[$i]["admin Id"];
        $aData[$i]["Name"] = $aAdmins[$i]["admin Name"];
        $aData[$i]["Status"] = $aAdmins[$i]["Status"];
        $aData[$i]["Created"] =$aAdmins[$i]["Created Date"];
        ++$i;
    }
}
if ($id) {
    
    $oSess->setAdminId($id);
    
    if (!strcmp($op, "del")) {
        
        $oSess->deleteAdmin();
        header("Location: index.php?path=1");
        
    } elseif (!strcmp($op, "act")) {
        
        $oSess->activateAdmin();
        header("Location: index.php?path=1");
        
    }  elseif (!strcmp($op, "deact")) {
        
        $oSess->deactivateAdmin();
        header("Location: index.php?path=1");
        
    } 
}

SetHead();
SetLeftMenu();
Bcontent();
?>

<table width="608" border="0" cellpadding="0" cellspacing="0">
    <tr>
        <td colspan="2"><div class="header">หน้าจอผู้ดูแลระบบเว็บไซต์ <?php print ENTITY ?></div></td>
    </tr>
    <tr>
        <td colspan="2"><div class="copy">กรุณาเลือกรายการที่ต้องการ</div></td>
    </tr>
    <tr>
        <td><div class="error"><?php ShowError() ?></div></td>
        <td align="right" valign="top"><?php if ($iPerm > 1) { ?><a href="form.php?op=add&path=1"><img src="../../_img/buttons/add.jpg" width="60" height="20" alt="" border="0" /></a><?php } ?></td>
    </tr>
</table>
<?php 
renderList($iCnt,$aData,$path); 
?>
<?php Econtent(); ?>