Connection to server closing while uploading files of 100mb

I'm uploading large files through an asp.net 1.1 web app... works fine on my
dev box and on a staging server with files up to about 300mb but on the live
box if I try to upload 100mb I get a page cannot be displayed with the
following info:

Explanation: The Web server connection was closed.
Error Code 64: Host not available
Background: The connection to the Web server was lost.

Both web.config's have the following:

<httpRuntime maxRequestLength="1048576" executionTimeout="3600"/>

My devbox is running IIS 5.1 (I think) on Windows XP Pro SP 2, the live
server is running Windows Server 2003 with IIS 6.

Thanks in advance for any suggestions.

--
Regards,

Phillip Johnson (MCSD For .NET)
PJ Software Development
www.pjsoftwaredevelopment.com