i have a web page that allows you to upload a file to the server.
if i upload a word document so the sever, then modify the original document and try to upload it again, the file overwrite fails.
does anybody know why.

if i do the same with either a text file or pdf file, the
file overwrite succeeds.

here is the code i am using

<%@ Control Language="vb" Inherits="dannet.uploadfile" %>
<%@ Import namespace = "System.IO" %>

    <script runat =server >





public sub upload_click (obj as object , e as eventargs )

      If Not (uploadedFile.PostedFile Is Nothing) Then


                Try

                    dim filepathname as string
                    filepathname = "./docs/" & filename
                    message.text = filepathname
                    postedFile.SaveAs(server.mapPath("./docs/") & filename)


                        Catch exc As Exception
                        message.Text = "Failed uploading file"
                End Try

    end if

    end sub


    </script>


        <table>
        <tr><td>

                        Select File to Upload: <input id="uploadedFile" size="60" type="file" runat="server" NAME="uploadedFile">
                        <Input Type="submit" Value="Upload" OnServerClick="Upload_Click" RunAt="Server" ID="uploaddoc" >



         </td></tr>
         <tr><td><asp:Label ID = message text = "" Runat = server />

         </td></tr>
        </table>