Cactus crashes Oracle Application Server

Hi,

I've got some servlet test case that work fine on Tomcat with the
ServletTestRunner but when I try to migrate them to OAS, the JVM crashes.
The big difference with the Tomcat environment is the front end server
(Oracle WebCache) that is involved in the request chain but I precise there
is no load balancing.
I read that cactus makes a double connection to the http server but I've no
idea which http server will be targeted, WebCache or the second http server.
Does the problem come from the WebCache ?

thanks for help.