IO / HTTP error in Uploadify

I am trying to get uploadify to work. When I try and upload something the browse functionality works fine but there is a breif pause and then I get either an "http error" or an "IO error".

The progress bar doesn't display, which made me think it might be a path issue, but the swf file is in the same location as the images / scripts which it appears to开发者_如何学Python be finding OK.

Anyone have any experience with this?

Did you use a generic handler (.ashx) for receiving the file? Here is my code

Public Class Video_File_Upload
    Implements System.Web.IHttpHandler
    'Dim File_Path_Chapter_Video As String = "XXX/"
    Dim Directory_Videos As String = System.Configuration.ConfigurationManager.AppSettings("Videos_Save")
    Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
        context.Response.ContentType = "text/plain"
        context.Response.Expires = -1
        Try
            Dim postedFile As HttpPostedFile = context.Request.Files("Filedata")
            Dim filename As String = postedFile.FileName
            'string folderName = context.Request.QueryString["FolderName"];
            Dim NOF As String
            Dim CheckFilePath As String
            Dim MapPath As String
            NOF = Convert.ToString(context.Request("NOF"))
            CheckFilePath = Directory_Videos & NOF
            If Directory.Exists(CheckFilePath) = False Then
                Directory.CreateDirectory(CheckFilePath)
            End If
            MapPath = Directory_Videos & NOF & "/" & filename
            postedFile.SaveAs(MapPath)
        Catch

        End Try
    End Sub

    ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
        Get
            Return False
        End Get
    End Property

End Class

Then you have to put this line in the upload setting: "uploadScript:Video_File_Upload.ashx"