Error when downloading big textfile with cfcontent

Hi,

I am running cf9 on Windows 2008 Server with IIS 7.5

I'm using  following code to download textfiles from the server:

<cfheader

    name="content-disposition" charset="utf-8"

    value="attachment; filename=textfile.txt"

    />

<cfcontent  type="text/plain"

    file = "#path#\textfile.txt" 

    deleteFile = "no">

This works very well, but when I try to download files bigger than approx. 80 MB I get the error:

Page not found.

The file I try to download is definitely there, so this cannot be the error.

Is there a limit in IIS or CF Administrator which blocks big files?

Or do I have to set the filesize in <cfheader>? (How?)

Please help!

Claudia