unable to deploy ear on weblogic 8.1 sp3

hi .
i have an application in struts 1.1 which was working fine in weblogic 8.1 sp3.
now i have upgraded to struts 1.2.8 and when i am trying to deploy the
applicaiton following error is thrown.

Unable to initialize Struts ActionServlet due to an unexpected exception or
error thrown, so marking the servlet as unavailable.  Most likely, this is due
to an incorrect or missing library dependency.
java.lang.NoSuchMethodError: <init>
        at
org.apache.commons.digester.Digester.<init>()V(Digester.java:150)
        at
org.apache.struts.action.ActionServlet.initServlet()V(ActionServlet.java:1111)
        at
org.apache.struts.action.ActionServlet.init()V(ActionServlet.java:328)
        at
javax.servlet.GenericServlet.init(Ljavax.servlet.ServletConfig;)V(GenericServlet
.java:258)
        at
weblogic.servlet.internal.ServletStubImpl$ServletInitAction.run()Ljava.lang.Obje
ct;(ServletStubImpl.java:1018)
        at
weblogic.security.acl.internal.AuthenticatedSubject.doAs(Lweblogic.security.subj
ect.AbstractSubject;Ljava.security.PrivilegedAction;)Ljava.lang.Object;(Authenti
catedSubject.java:321)
        at
weblogic.security.service.SecurityManager.runAs(Lweblogic.security.acl.internal.
AuthenticatedSubject;Lweblogic.security.acl.internal.AuthenticatedSubject;Ljava.
security.PrivilegedAction;)Ljava.lang.Object;(SecurityManager.jav
        at
weblogic.servlet.internal.ServletStubImpl.createServlet()Ljavax.servlet.Servlet;
(ServletStubImpl.java:894)
        at
weblogic.servlet.internal.ServletStubImpl.createInstances()V(ServletStubImpl.jav
a:873)
        at
weblogic.servlet.internal.ServletStubImpl.prepareServlet(Lweblogic.servlet.inter
nal.RequestCallback;)V(ServletStubImpl.java:812)
        at
weblogic.servlet.internal.WebAppServletContext.preloadServlet(Ljava.lang.String;
)V(WebAppServletContext.java:3281)
        at
weblogic.servlet.internal.WebAppServletContext.preloadServlets(Ljava.util.Vector
;)V(WebAppServletContext.java:3238)
        at
weblogic.servlet.internal.WebAppServletContext.preloadServlets()V(WebAppServletC
ontext.java:3224)
        at
weblogic.servlet.internal.WebAppServletContext.preloadResources()V(WebAppServlet
Context.java:3207)
        at
weblogic.servlet.internal.HttpServer.preloadResources()V(HttpServer.java:694)
        at
weblogic.servlet.internal.WebService.preloadResources()V(WebService.java:483)
        at
weblogic.servlet.internal.ServletInitService.resume()V(ServletInitService.java:3
0)
        at
weblogic.t3.srvr.SubsystemManager.resume()V(SubsystemManager.java:131)
        at weblogic.t3.srvr.T3Srvr.resume()V(T3Srvr.java:966)
        at weblogic.t3.srvr.T3Srvr.run([Ljava.lang.String;)I(T3Srvr.java:361)
        at weblogic.Server.main([Ljava.lang.String;)V(Server.java:32)

I have checked the digester and the clas spath. i am using the digester-1.6
which is shipped with struts 1.2.8

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