Index: branches/5.2.x/core/admin_templates/js/grid_filters.js
===================================================================
diff -u -N -r16552 -r16620
--- branches/5.2.x/core/admin_templates/js/grid_filters.js	(.../grid_filters.js)	(revision 16552)
+++ branches/5.2.x/core/admin_templates/js/grid_filters.js	(.../grid_filters.js)	(revision 16620)
@@ -133,7 +133,7 @@
 
 MultiOptions.ItemChecked = function(selector_index) {
 	// sync hidden field
-	var $reg_exp = new RegExp('^_mutlioptions_cb_' + selector_index + '_(?!all)([0-9A-Za-z-]+)');
+	var $reg_exp = new RegExp('^_mutlioptions_cb_' + selector_index + '_(?!all)([0-9A-Za-z-_]+)');
 	update_checkbox_options($reg_exp, MultiOptions.Selectors[selector_index]);
 
 	// update "Select All" checkbox
@@ -160,6 +160,6 @@
 	});
 
 	// sync hidden field
-	var $reg_exp = new RegExp('^_mutlioptions_cb_' + selector_index + '_(?!all)([0-9A-Za-z-]+)');
+	var $reg_exp = new RegExp('^_mutlioptions_cb_' + selector_index + '_(?!all)([0-9A-Za-z-_]+)');
 	update_checkbox_options($reg_exp, MultiOptions.Selectors[selector_index]);
 }