streaming data & xp

[ann]

The server is windows 2000 & IIS 6. When I stream my pdf and view in 2000 it
works fine, the pdf opens and everything looks great - in xp the page is
blank. If the user refreshes the page, they get the following:

(blank gif)

Here is my code:
.......
Response.ContentType = "application/pdf";
// IE & Acrobat seem to require "content-disposition" header being in the
response.
// If you don't add it, the doc still works most of the time, but not always.
// this makes a new window appear:
// Response.AddHeader("content-disposition","attachment; filename=MyPDF.PDF");
Response.AddHeader("content-disposition","inline; filename=CompLetter.PDF");
// Create the PDF export object
PdfExport pdf = new PdfExport();
// Create a new memory stream that will hold the pdf output
System.IO.MemoryStream memStream = new System.IO.MemoryStream();
// Export the report to PDF:
pdf.Export(rptBlank1.Document, memStream);
// Write the PDF stream out
Response.BinaryWrite(memStream.ToArray());
// // Send all buffered content to the client
Response.End();

Anyone know why and how I can fix this? The users need to experience the
same on xp as it works on 2000. It appears this is isolated to xp, but I
haven't a clue what to do.

Any help would be appreciated - thanks!