I assume you are using AS6? If so, you don't need to add validation-api.jar to the classpath.
http://dict.leo.org/ende?lp=ende&p=Ci4HO3kMAA&search=Regrettably&trestr=0x8080we use a JBoss 4.2, more precisely the JBoss Portal 2.7.2.
Regrettably, our customer wouldn't change to AS6, because they have too many applications on AS4.2.
An extra AS6 don't come into consideration, too.
So I assume you followed the Upgrade JBoss AS to JSF2?
It sounds like you aren't planning to use Bean Validation. So why are you adding the jar for it?
If you do want to use BV, you'll need to add the BV API and implementation. Then add this code to a ServletContextListener in your WAR:
This is all vary hacky and unsupported for AS 4.2. If you want to post the fuill stack trace I might be able to help some but I won't be able to spend a lot of time on helping you get this to work.