JBoss AS 4.0.5 ships with MyFaces 1.1.4.
MyFaces 1.1.5 contains several bug fixes including an important one for the MyFaces Portlet Bridge. If you are using JBoss Portal in a production environment, it is recommended that you upgrade MyFaces to version 1.1.5.
Download MyFaces 1.1.5 from the MyFaces web site.
In your JBoss 4.0.5 installation, go to deploy/jbossweb-tomcat55.sar/jsf-libs
According to the MyFaces website, commons-beanutils 1.7 is a requirement of MyFaces 1.1.5 - you might therefore have to upgrade this, too.
You will need to rename the MyFaces jars that are downloaded. Rename myfaces-api-1.1.5.jar to myfaces-api.jar and myfaces-impl-1.1.5.jar to myfaces-impl.jar.