pls. solve my problem

My problem is i am upgrading my project from  weblogic 7.0 to weblogic  9.0.
firstly i have directly  tried to deploy my ear file of weblogic 7.0 to weblogic
9.0
but i got error regarding web.xml  so i have used  weblogic 9.0 's java
weblogic.marathon.ddinit.WebInit utility
& i got new web.xml & weblogic.xml.
           again i have created my ear file & checked it for error using
java weblogic.appc utility for any error & i got unmarshled error.
[u]Stack Trace:[/u]
weblogic.descriptor.DescriptorException: Unmarshaller failed
        	at
weblogic.descriptor.internal.MarshallerFactory$1.createDescriptor(Mar
		shallerFactory.java:149)
        	at
weblogic.descriptor.DescriptorManager.createDescriptor(DescriptorMana
		ger.java:254)
       	at
weblogic.descriptor.DescriptorManager.createDescriptor(DescriptorMana
		ger.java:283)
        	at
weblogic.application.descriptor.AbstractDescriptorLoader.createDescri
		ptor(AbstractDescriptorLoader.java:344)

  
  can u help me reagrding this matter pls. psl. help me
    Thanks in advance

[b]can any body tell me what changes need to be done while migrating to weblogic
9.0 from weblogic 7.0 or weblogic 8.0[/b] 

reagrds