Can't Assign Values to Textbox inside updatepanel.

Hi Guys,

I have panel control and inside panel control I have update panel and inside update panel I have few textboxes.  The problem is  I am not able to change the values on the Page_Load event on first page load (not post back).  

Can anyone help me out with this?

protected void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  { 
      txtPW1.Text = "567890";   
      txtPW2.Text = "567890";
  }
}

<asp:Panel runat="server" ID="pnUserInfo" Width="95%" 
            GroupingText="<span class=grpTitle>Entry Information</span>"><asp:UpdatePanel ID="upUserInfo" runat="server"><ContentTemplate><table cellpadding="3" cellspacing="0" style="width: 100%"><tr><td align="right" class="tdText">
                                User ID<span style="color: #FF0000 !important">*</span></td><td align="right"><asp:TextBox ID="txtUserName" runat="server" CssClass="txtBox" onkeypress="return AllowForUserName(event);"
                                    onpaste="return false;"  MaxLength="30" AutoPostBack="True" OnTextChanged="OnUserNameChanged" Enabled="False"></asp:TextBox><%--  <asp:Image ID="imgUserAv" runat="server" ImageUrl="~/_Images/User.png" Width="20px" />--%></td><td colspan="2"><asp:Label ID="lblUserAvailStatus" runat="server" Width="85%"></asp:Label></td></tr><tr><td align="right" class="tdText" style="width: 140px">
                               Password<span style="color: #FF0000 !important">*</span></td><td align="right"><asp:TextBox ID="txtPW1" runat="server" TextMode="Password" CssClass="txtBox" onpaste="return false;"
                                     MaxLength="24"></asp:TextBox></td><td align="right" class="tdText" style="width: 140px">
                              Re-enter Password<span style="color: #FF0000 !important">*</span></td><td align="right"><asp:TextBox ID="txtPW2" runat="server" TextMode="Password" CssClass="txtBox" onpaste="return false;"
                                     MaxLength="24"></asp:TextBox></td></tr></table></ContentTemplate></asp:UpdatePanel></asp:Panel>