รบกวนดู code ค้นหาข้อมูลที่ค่ะมันขึ้น Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in .... on line 21 ต้องแก้ตรงไหนค่ะช่วยชี้แนะด้วย

<?
$objConnect = mysql_connect("localhost","root","") or die("Error Connect to Database");     
$objDB = mysql_select_db("training_system");
?>
<form id="form1" name="form1" method="GET" action="se_3.php" enctype="multipart/form-data">
<p>user  <input name="txtKeyword" type="text" id="txtKeyword" value="<?=$_GET["txtKeyword"];?>" /></p>
<p><input name="Search" type="submit" value="ค้นหา" /></p>
</form>
  <? 
if($_GET["txtKeyword"] != "")     
{    
$objConnect = mysql_connect("localhost","root","") or die("Error Connect to Database");     
$objDB = mysql_select_db("training_system");     
// Search By Name or Email     
$strSQL1 = "SELECT * FROM user WHERE (username LIKE '%".$_GET["txtKeyword"]."%')";    
$objQuery = mysql_query($strSQL1) or die ("Error Query [".$strSQL1."]");  
}   
?>
<table width="220" border="1" cellspacing="1" cellpadding="1">
<?    
while($objResult = mysql_fetch_array($objQuery))     
{     
?>
<tr>
<td width="148" height="28" valign="top"><span class="style1"><?=$objResult["username"];?></span></td>
</tr>
<?
}
?>
</table>