Problem with HTTP Keepalives with Tomcat 5.0 and IIS 6.0

We have a problem with HTTP keepalive requests not being honoured from the a .NET forms application connecting to a Tomcat 5.0.25 server via an IIS 6.0 server using the Tomcat Isapi filter (v1.2.25).  The Website is set to use NTLM via the "NTAuthenticationProviders" Metabase parameter.

We get the same problem if we use IE as the client to connect to the Tomcat application.  The HTTP headers show the keepalive request being asked for by the client but every request is re-authenticated by IIS despite "HTTP Keepalives" being ticked in the website properties.  I suspect it is the Tomcat ISAPI filter that is closing the session but can't find any way to configure it not to do this.

If the Tomcat ISAPI filter isn't installed on the website then the keepalives work as expected and you only authenticate once against IIS per session.  Also if Tomcat is handling the NTLM authentication using JCIFs then again you only authenticate once.

This isn't a huge problem for users in the same datacentre as the application as the NTLM authentication happens reasonably quickly but for users in a remote DC this is adding 1.5s to every request which is unacceptable.

Any help appreciated!

Thanks