I attached an event handler to certain buttons, that altered the settings of the validator object on that particular form.
$(".jsCancel").click(function (e) {
$(e.currentTarget).closest("form").validate().settings.ignore = "*"
});
This has worked like a charm for me in MVC3.
I don't know if this helps you in particular, but since I use ajax form, I had to attach the event to these buttons each time the contents of the ajax form was replaced, by using the event ajax success. The full code that reparses the form and attaches the event to the cancel buttons is:
$(document).ajaxSuccess(function (event, xhr, settings) {
var $jQval = $.validator, adapters, data_validation = "unobtrusiveValidation";
$jQval.unobtrusive.parse(document);
$(".jsCancel").click(function (e) {
$(e.currentTarget).closest("form").validate().settings.ignore = "*"
});
});