Running Jboss 3.0.3/Tomcat 4.1.X

I never see this in normal mode, but when I try to start in debug mode (options -classic -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,address=8787,server=y,suspend=n), I usually (but not always) get:

11:36:52,777 ERROR [Server] start failed
org.jboss.deployment.DeploymentException: instantiating org.jboss.security.auth.login.XMLLoginConfig failed: java.lang.NoClassDefFoundError: org/jboss/security/
auth/login/XMLLoginConfigImpl; - nested throwable: (RuntimeErrorException: instantiating org.jboss.security.auth.login.XMLLoginConfig failed: java.lang.NoClassDefFoundError: org/jboss/security/auth/login/XMLLoginConfigImpl
Cause: java.lang.NoClassDefFoundError: org/jboss/security/auth/login/XMLLoginConfigImpl)

I may get this 5 times in a row, and then the 6th will come up OK. Or not. Or the 3rd may work. What should I be looking for?