Thanks for answering mate.
In fact, we already solved the problem. We implemented a new view handler and appointed it on faces-config.xml. It's source code was identical to 1.2_03's version of ViewHandlerImpl.java + the 480 issue bug fix. It's been working great so far.
I hope this can help others with similar incompatibility issues.
[Message sent by forum member 'lalkmim' (lalkmim)]
http://forums.java.net/jive/thread.jspa?messageID=348688