I'd like to see a "validation in error" event for form. It would have helped me in many case.
I'm providing a patch that should work. If Anything else can be done, I'll be glad to help.
FYI, we talk about this a long time ago here: http://apache-tapestry-mailing-list-archives.1045711.n5.nabble.com/Prevent-double-or-more-submissions-td5729405.html