Internet Explorer problems downloading files from IIS 6 - Response.AddHeader("content-disposition", ...)

I'm retrieving a file from my DB, storing in a Byte[] variable. In my local development environment, Visual Studio 2008, the file download works great in all browsers (IE, Firefox, and Chrome).
But, when running on external IIS 6.0 web server, IE 7 and IE 8 browsers will not properly download files: the indicated file name seems to default to my ASPX page "[template].aspx" , not the file name that I specify in the Response.AddHeader(...). 
FIREFOX and CHROME download all files, all MIME types JUST FINE with the correct file name. This problem occurs only in IE? (Several clients all tested with same results.) Is there a disconnect between IE and IIS 6.0 in how the response headers are interpreted? Is there another header attribute needed for IE?

My code:
    Response.Clear();
    Response.ClearHeaders();
    Response.Buffer = true;
    Response.ContentType = ...