The only suspicious classes may interfere with Tomcat belong to org.w3c package in ss_css2.jar. Try to temporarily remove ss_css2.jar. Does it block or throw an exception in the case?

Another point is that PD4ML uses AWT classes (for example, fonts). In server-side scenarios it requires headless mode of JVM. Make sure Tomcat runs with -Djava.awt.headless=true JVM parameter.