menu hook

your need to wrap the contents og your hook_menu within a if (!$may_cache) block in order to prevent those stylesheets and js from being adde twice. not a big deal. module looks nice so far.

here is the change

// Implemention of hook_menu()
function nice_menus_menu($may_cache) {
  if (!$may_cache) {
    drupal_add_js(drupal_get_path('module', 'nice_menus').'/nice_menus.js');
    theme_add_style(drupal_get_path('module', 'nice_menus').'/nice_menus.css');
  }
}