after page loads with a struts property with null object before the 'GET' sample(product.info.size where info come null) the page compilance fails and wont work anymore even with all correct values

after a page loads with a struts property with null object:
sample(<html:hidden property="product.info.size" /> where info come null)
the page compilance fails and wont work anymore even with all correct values
the page back to work restarting jboss or deleting .class of the page
it dont happens in jboss version 4.0.0