ajax.js: fix a cache problem: clicking back sometimes makes submit button disabled

js/ajax.js

@@ -15,6 +15,9 @@ $(window).ready(function() {
 	var settings = new script_settings('ajax');
 	var do_not_ajax = false;
 
+	// Enable submit button if disabled (cache problem)
+	$('input[type="submit"]').removeAttr('disabled');
+	
 	var setup_form = function($form) {
 		$form.submit(function() {
 			if (do_not_ajax)