I've been trying out this combo of Tomcat 4.0
(running separately) with JBoss as well
and have found a couple of a things to check
to ensure no JNDI related problems when
accessing EJBs from servlets -
a) the servlet webapp has the
and jboss-client.jar in the WEB-INF/lib directory
b) Tomcat is started with the -nonaming option.
You can edit the startup.bat/startup.sh
in the bin directory of the installation
call "%EXECUTABLE%" start -nonaming %CMD_LINE_ARGS%
let me know if this works for you.