Invalidating continuations doesn't work?

[Hunsberger, Peter]

In order to stop a user from submitting an insert (or delete) twice I'm
attempting to use some flow script like the following:

    var k = cocoon.sendPageAndWait( page, args );     
    var action = _getAction();
    if ( action.startsWith("cocoon-action-Insert")  )   {        
        k.invalidate();
    }
        .
        .
        .

Adding some debug statements shows that the script is executing as
expected.  However, if the user hit's the back button and resubmits the
continuation appears to get reinvoked.  Am I missing something in the
way invalidate works?  I thought I'd get a continuation does not exists
type of error?  Is this perhaps a bug in the 2.1.3 code branch?

Peter Hunsberger