MaskedEditExtender not displaing the data

Question

Ajax MaskedEditExtender is not displaying data when page gets loaded i set the value of TextBox and MaskedEditExtender as shown below :

<asp:TextBox ID="txtFromTime" runat="server" Width="60"></asp:TextBox>                        
<asp:MaskedEditExtender ID="mexFromTime" runat="server" TargetControlID="txtFromTime" Mask="99:99:99" MaskType="Time" />
<asp:MaskedEditValidator ID="MaskedEditValidatorFromTime" runat="server" 
                        ControlExtender="mexFromTime" ControlToValidate="txtFromTime" 
                        InvalidValueBlurredMessage="*" MaximumValueBlurredMessage="*" 
                        MinimumValueBlurredText="*" Display="Dynamic" ErrorMessage="*"  />

and then in code i have done this :

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {               
            this.txtFromTime.Text = "00:00:00";
        }
    }

In Windows 7 where i have created this web application the 00:00:00 gets appeard in txtFromTime textbox but in windows XP txtFromTime is empty.

Any suggesstions to make it work in XP?