ระบบสมาชิก เปลี่ยน Password แล้วไม่ Update อะครับช่วยทีครับ

<?
@session_start();
ob_start();
$usermem = $_SESSION["usermem"];
require_once "include/connectdb.php";
require_once "include/connect.php";
require_once "include/tdate.php";
if(empty($usermem)) 
{
$showmember = "
<table width=227 border=0 cellspacing=1 cellpadding=1>
                    <form method=post action=SignIn.php><tr> 
                      <td width=50><div align=right><img src=images/icon_register.gif width=25 height=17></div></td>
                      <td width=170><input name=usermem type=text class=inputx size=13 sizze=12></td>
                    </tr>
                    <tr> 
                      <td><div align=right><img src=images/database.gif width=16 height=20></div></td>
                      <td><input name=passmem type=password class=inputx id=passmem size=13 sizze=12></td>
                    </tr>
                    <tr> 
                      <td>&nbsp;</td>
                      <td><input name=submit type=submit class=submit value=เข้าระบบ></td>
                    </tr>
                    <tr>
                      <td>&nbsp;</td>
                      <td><img src=images/plus.gif width=11 height=11> <font size=2><a href=MemberRegister.php>สมัครสมาชิก</a></font></td>
                    </tr></form>
                  </table>
";
}else{
$sql="select * from member where usermem='$usermem'";
						  $db_query=mysql_db_query($db,$sql);
						  $result=mysql_fetch_array($db_query);
						  $idxx=$result[id];
						  $usename=$result[name];
						  $user_mem=$result[usermem];
						  $pass_mem=$result[passmem];
$showmember = "