When I click a command button, and then hit the browser back button to the form and click it again, it submits a second time without throwing the proper exception...

Even stranger, the form id itself is DIFFERENT when I come back, which implies it has regenerated a "valid" form id at some point.

Here's the relevant code: Any ideas?

<h:form id="accountActivationForm">
    <s:token/>
    <a4j:commandButton id="cancelActivateAccountButton"
        action="#{controller[cancelAction]}"
    image="/images/button-Cancel-gray.gif"
        reRender="#{reRenderList}"
        oncomplete="#{onCancelComplete}" />
        &#160;
    <a4j:commandButton id="activateAccountButton"
        action="#{controller[agreeAction]}"
        image="/images/button-i-agree-continue.gif"
        styleClass="activate-account-button"
        reRender="#{reRenderList}"
        oncomplete="#{onActivationComplete}"/>
</h:form>

Clarifications:

• I inherited this, so I'm trying to change it as little as possible. (It's used in a couple places.)
• Each action returns a view, not null. I have confirmed this by stepping through line-by-line.
• The reRenderList is empty in my current test-case.
• onActivationComplete is also empty.

I'm going to be going template-by-template to see if someone made it with nested forms, because my coworkers have had unrelated problems due to that, so it couldn't hurt to eliminate that as a possible problem.