IIS 6.0 & 2003 server- connection keeps getting dropped

Hi,
I keep getting disconnected with a Connection_Dropped message in the HTTPErr log whenever an out of process call returns a string output very big in size (20MB)...the connection drops when the Response.Write call is made to send back the string. I have set the aspbufferlimit to 64MB for testing, but it had no effect. I checked the "IsClientConnected" property before the write call, and it is true. It works fine on Win2k with iis 5.*, but not in Windows 2003 server with IIS 6.0. The script/session timeouts are all set to 20 minutes (the transaction takes less than a minute). The Response is being sent back to an XMLHTTP request.
Any ideas?

Thanks,
manny

'----global asa-------

Sub Session_OnStart
Set Session("oMyObj") = Server.CreateObject("MyLib.MyObj")
End Sub

'-----myASP.asp---------
<%
Option Explicit
Dim oMyObject
Dim sResponse

Set oMyObject = Session("oMyObj")

' I am getting a Connection_Dropped message in HTTPErr when
' this function call below returns 20Megs of data (4-5 megs work fine)

sResponse = oMyObject.LongRunningFunction(someParameter)

Response.Write sResponse
%>