XML file that is read/written to disappears from server -- help wanted

[mortb]

My problem is with a XML file that resides on my windows 2003 web server.
I have this user control which I include on every page in my applicaiton.
The control makes it possible for the users to leave feedback when using the page.
The feedback is written to a XML file which I have put in a folder "C:/Save/".
I've set the access rights on this folder so that the "IUSR_MachineName" has full rights on this folder and it's children.

The "c:/save" folder is included as a virutal folder in the application i.e. /webApplciation/save
All this works fine. The coments are saved along with some other information from server variables.
I've tested and I can both leave a comment and read the given comments in the xml file.
The problem is when I've left the computer running for a while the XML file mysteriously disappears.

Any ideas? I wonder if this is due to some sequrity settings ont win2003 server that I'm not avare of?
I've included the control code and XML file below.

cheers,
mortb

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leaveComment.ascx:


<%@ Control language="c#" Codebehind="leaveComment.ascx.cs" AutoEventWireup="false" Inherits="controls.leaveComment" %>
<asp:LinkButton ID="_lnkShowComments" Runat="server">Give feedback...</asp:LinkButton>
<asp:LinkButton ID="_lnkHideComments" Runat="server" Visible="False" EnableViewState="False">Hide</asp:LinkButton>
<br>
<asp:TextBox id="_txtComments" runat="server" Height="159px" Width="421px" Visible="False" EnableViewState="False" TextMode="MultiLine"></asp:TextBox>
<br>
<asp:Button ID="_btnAddComment" Text="Submit" Runat="server" Visible="False" />
<asp:Label id="lblThx" runat="server" Visible="False"><h3>Thank you!</h3></asp:Label>

--------------------------------------------------------------------------------------------------------------------------------

leaveComment.ascx.cs

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Xml;

namespace controls
{
public class leaveComment : System.Web.UI.UserControl
{
protected System.Web.UI.WebControls.Button _btnAddComment;
protected System.Web.UI.WebControls.Label lblThx;
protected System.Web.UI.WebControls.LinkButton _lnkShowComments;
protected System.Web.UI.WebControls.LinkButton _lnkHideComments;
protected System.Web.UI.WebControls.TextBox _txtComments;


#region Web Form Designer generated code
override protected void OnInit(EventArgs e)
{

InitializeComponent();
base.OnInit(e);
}

private void InitializeComponent()
{
this._lnkShowComments.Click += new System.EventHandler(this._lnkShowComments_Click);
this._lnkHideComments.Click += new System.EventHandler(this._lnkHideComments_Click);
this._btnAddComment.Click += new System.EventHandler(this._btnAddComment_Click);

}
#endregion

private void _btnAddComment_Click(object sender, System.EventArgs e)
{

XmlDocument oXml = new XmlDocument();
oXml.Load(Server.MapPath("/webApplciation/save/comments.xml"));

XmlNode oNode = oXml.SelectSingleNode("/xml/comments");
XmlElement elem = oXml.CreateElement("comment");

XmlAttribute oAttPage = oXml.CreateAttribute("page");
oAttPage.Value = Server.UrlEncode(Request.Path) ;
elem.Attributes.Append(oAttPage);

XmlAttribute oAttQString = oXml.CreateAttribute("QueryString");
oAttQString.Value = Server.UrlEncode(Request.QueryString.ToString());
elem.Attributes.Append(oAttQString);

/*
XmlAttribute oAttForm = oXml.CreateAttribute("Form");
oAttForm.Value = Request.Form.ToString();
elem.Attributes.Append(oAttForm);
*/

XmlAttribute oDate = oXml.CreateAttribute("time");
oDate.Value = Server.UrlEncode(System.DateTime.Now.ToString());
elem.Attributes.Append(oDate);

elem.InnerText = _txtComments.Text;
oNode.AppendChild(elem);

oXml.Save(Server.MapPath("/webApplciation/save/comments.xml"));

_btnAddComment.Visible = false;
_txtComments.Visible = false;

lblThx.Visible = true;

}

private void _lnkShowComments_Click(object sender, System.EventArgs e)
{
_lnkHideComments.Visible =
_txtComments.Visible =
_btnAddComment.Visible = true;

_lnkShowComments.Visible = false;
}

private void _lnkHideComments_Click(object sender, System.EventArgs e)
{
_lnkShowComments.Visible = true;

_lnkHideComments.Visible =
_txtComments.Visible =
lblThx.Visible =
_btnAddComment.Visible = false;
}
}
}

--------------------------------------------------------------------------------------------------------------------------
comments.xml:


<?xml version="1.0" encoding="utf-8"?>
<xml>
<comments>
</comments>
</xml>