Filter Exception no webwork

Olá. Estava trabalhando normalmente com o webwork 2.2.2, mas agora não consigo mais startar a aplicação… ocorre aseguinte exception no console do tomcat:

SEVERE: Exception starting filter webwork java.lang.NullPointerException at com.opensymphony.webwork.dispatcher.FilterDispatcher.getActionResultConfig(FilterDispatcher.java:207) at com.opensymphony.webwork.dispatcher.FilterDispatcher.init(FilterDispatcher.java:144) at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:223) at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:304) at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:77) at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3600) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4189) at org.apache.catalina.manager.ManagerServlet.start(ManagerServlet.java:1175) at org.apache.catalina.manager.HTMLManagerServlet.start(HTMLManagerServlet.java:527) at org.apache.catalina.manager.HTMLManagerServlet.doGet(HTMLManagerServlet.java:104) at javax.servlet.http.HttpServlet.service(HttpServlet.java:689) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:524) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684) at java.lang.Thread.run(Unknown Source)

Alguém sabe o que pode estar causando esse problema ?

Valeu!