Index: branches/RC/core/units/categories/categories_event_handler.php
===================================================================
diff -u -N -r11610 -r11635
--- branches/RC/core/units/categories/categories_event_handler.php	(.../categories_event_handler.php)	(revision 11610)
+++ branches/RC/core/units/categories/categories_event_handler.php	(.../categories_event_handler.php)	(revision 11635)
@@ -1641,7 +1641,7 @@
 
 		$fields = $this->Application->getUnitOption($event->Prefix, 'Fields');
 		$theme_id = $this->_getCurrentThemeId();
-		$fields['ParentId']['default'] = $this->Application->GetVar('m_cat_id');
+		$fields['ParentId']['default'] = (int)$this->Application->GetVar('m_cat_id');
 		$fields['ParentId']['options'] = $this->_printChildren($data, $root_category, $this->Application->GetVar('m_lang'), $theme_id);
 
 		// limit design list by theme