<s:decorate> renders a DIV surrounding the template, which of course is invalid HTML where you are trying to use it - hence the lack of rendering.
<ui:decorate> does not do this so maybe try that instead.
thanks for the answer - that's a good point.
it works fine in a non-ajax environment, but i guess this doesn't mean too much. i tried uideorate, but this didnt trigger validation at all...
i found this quote of pete muir (https://jira.jboss.org/jira/browse/JBSEAM-1572)
s:decorate gives you 2 things over ui:decorate * putting a span around it's contents, making it targetable by a4j * adding some custom, scoped to the decorate, parameters (invalid, required).
i'll try to use explicite a4j next...
solved it with ui:decorate...
only drawback is that i cannot use the implicite objects (required, invalid)