Different locales depending on user's settings (browser) do not work during runtime of the application.
Preconditions: There are two resource bundles for the menu (Menu_en.properties, Menu_de.properties).
Symptoms: Say, the user has English set in the browser.
When the application is first started, a resource bundle is correctly loaded for the first locale that comes from the browser.
However, if a different locale is sent, the first resource bundle is used instead of the right one.

Some research shows that the class net.sf.navigator.taglib.UseMenuDisplayerTag reuses the resource bundles no matter if the locale changed.
The problem seems to be in line 203:

if (rb != null) {
mrDisplayerInstance.setMessageResources(rb);
} else {

Two solutions come to my mind:
a) put each resource bundle in a map; key is the locale; problem: locales without resources must be mapped to a default locale
b) save the last active locale and check if the locale changed since the last request