Is there a size restriction in Response.OutputStream

I'm using the technic described in: http://support.microsoft.com/kb/812406
to allow users to download files.  Our group uses a tool called SecureGateway which doesn't seem to like FTP as a protocol.
Smaller files don't seem to have a problem, but intermittently larger files (larger than 10K) will not download to the client properly.  They will just abruptly end the transfer as if they are actually completed.
 
I use the following code:
 
 
 

 
{
     System.IO.
Stream iStream = null;// Buff ...