migration to JBoss 5.1 - Failed to create a new SAX parser

Question

I am trying to deploy my application (packed in .war file) that work properly on JBoss 4.2.3 to JBoss 5.1 (using java 5).

Currently during deployment time I see in the server.log the error:

... Caused by: org.jboss.xb.binding.JBossXBRuntimeException: Failed to create a new SAX parser

... Caused by: java.lang.ClassCastException: org.apache.xerces.parsers.XML11Configuration

According to this thread in JBoss forums, I need to isolate my application. My questions:

1. according to JBoss 5.1 Release Notes - The major differences with the existing configurations is that call-by-value and deployment isolation are enabled by default. Therefore do I really need implicitly set my application isolated?
2. I thought that isolation is mainly needed when the same application server runs several applications that collides with each other. In my case I am trying to run only one application. So again is the isolation required?
3. If the answer is positive to the above question and I need to enforce isolation - how can I configure it? suppose my war file is called 'foo'. do I have to insert to the jboss-web.xml the section:

<jboss-web> 
  <loader-repository>
 tld.mydomain:loader=foo.war
 </loader-repository>
</jboss-web>

Answer 1

OK Apperently the solution is to remove xerces.jar from my web-inf/lib

Isolation won't work due to some bug. See here