Amazon S3 File Download/Open Error

I am currently using an HTTP handler in an attempt to serve up a file from my S3 bucket. I am not getting an error, but the first run through always fails. The file gets "served" to the webpage and the typical "Open or Save" message appears. If I click "Save", everything works as it should. If I click "Open", however, it simply says that the file could not be downloaded. "Retry" is an option at this point. If I click "Retry" the file opens normally. This happens -EVERY- time. I'm not sure what I'm doing wrong. If anyone has any insight after reviewing my code below, PLEASE help me out.

            Dim awsBucket As String = ConfigurationManager.AppSettings("AWSFiles")
            Dim awsS3KeyId As String = ConfigurationManager.AppSettings("AWSS3KeyId")
            Dim awsS3Key As String = ConfigurationManager.AppSettings("AWSS3Key")
            Dim client As AmazonS3Client = New AmazonS3Client(awsS3KeyId, awsS3Key, Amazon.RegionEndpoint.USEast1)
            Dim guidFileGUID As New Guid(context.Request.QueryString("GUID"))
            Dim guidConv As New GuidConverter
            Dim dtFiles As New DataTable

            dtFiles = MyData.ProcTable("GetFiles", "@Files", guidConv.ConvertToString(guidFileGUID))

            If dtFiles.Rows.Count > 0 Then
                Dim reqS3Request As New GetObjectRequest
                Dim strOriginalFileName As String = dtFiles(0)("OriginalFileName")
                Dim strFileName As String = guidConv.ConvertToString(dtFiles(0)("FileID")) & System.IO.Path.GetExtension(strOriginalFileName)

                reqS3Request.BucketName = ConfigurationManager.AppSettings("AWSFiles")
                reqS3Request.Key = User.CorpID & "/" & strFileName

                Dim respS3Response As GetObjectResponse = client.GetObject(reqS3Request)

                Using myStream As System.IO.Stream = respS3Response.ResponseStream
                    Dim intStreamLength As Integer = myStream.Length
                    Dim bytFile(intStreamLength - 1) As Byte
                    Dim intBytesToRead As Integer = intStreamLength
                    Dim intBytesRead As Integer = 0

                    Do
                        Dim intChunkSize = 1000

                        If intChunkSize > intBytesToRead Then intChunkSize = intBytesToRead

                        Dim i As Integer = myStream.Read(bytFile, intBytesRead, intChunkSize)

                        intBytesRead += i
                        intBytesToRead -= i
                    Loop While intBytesToRead > 0

                    context.Response.Buffer = True
                    context.Response.Clear()
                    context.Response.ContentType = GetMimeType(strFileName)
                    context.Response.AddHeader("content-disposition", ("attachment; filename=" & strOriginalFileName))
                    context.Response.BinaryWrite(bytFile)
                    context.Response.Flush()
                    context.Response.Close()
                End Using

A bit of background.

• Majority portion of code found at and modified from http://ift.tt/17kCW7h


• Files are uploaded to S3 with a new name, which is a GUID. The file information, including original filename, is stored in our database.


• Sproc "GetFiles" gets the file information stored in our database.


• Function "GetMimeType" uses a cached datatable to look up the HTTP encoded mime-type for the given file.


• There used to be a "context.Response.End()" between Flush and Close, but I kept getting an error saying the thread was being aborted.

Here's the standard message that comes up when I click the file link. Here's the message that comes up when I click "Open" in the previous image. If I click "Retry" from here, it works just fine.