Hi

Please check this thread about the validation controls:

http://cutesoft.net/forums/thread/47402.aspx

You can use Uploader1.InsertButton.ValidationGroup = "NoNeed";
 to prevent the validation control stop the uploader doing the postback.

That should help you to fix the 1-3 questions.
(you do not need disabled the validation controls while uploading)

I suggest you use the UploadPersistedFile control so that you can use the uploaded file as :

protected void LinkButton1_Click(object sender, EventArgs e)
{
    PersistedFile file=UploadPersistedFile1.File;
    if(file!=null)
    {
        //file.MoveTo...
    }
}

about check whether a file have been uploaded, you can check this thread:

http://cutesoft.net/forums/thread/47404.aspx

You can do this way:

<asp:UpdatePanel>
<ContentTemplate>
<CuteWebUI:UploadPersistedFile id=UploadPersistedFile1... />
<asp:TextBox runat=server id=TextBox1 />
</ContentTemplate>
</asp:UpdatePanel>
<script runat=server>
protected override void OnPreRender(EventArgs args)
{
    PersistedFile file=UploadPersistedFile1.File;
    TextBox1.Style["display"]="none";
    TextBox1.Text=(file==null?"false":"true");
}
</script>
<script>
var theboxid='<%=TextBox1.ClientID%>';
function HasUploadedFile()
{
    var box=document.getElementById("theboxid");
    return box.value=="true";
}
</script>

Regards,
Terry