I, or actually Claus from CB Computerservice in Austria, has discovered a bug in the Quick Locale Switcher which could in some way be potentially dangerous. The problem is that switching to certain locales could disable the automatic updating system in Firefox and Thunderbird. What happens is when you switch to a locale that is not available as a translation of your Mozilla application, for example de-AT when only a de version is available, the automatic update manager will not be able to find any updates for your application. The automatic update manager in the Mozilla applications check for an update available in the locale in which you originally installed it by reading the general.useragent.locale preference, and if it can not find any, because you switched to a too specific locale using the Quick Locale Switcher, you will not be notified about an update. The workaround for this problem is to create a custom locale with a general language code like de (instead of de-AT) or fr (instead of fr-FR), switch to this language using the QLS, and then manually check for updates using the Check for updates menu item in the Help menu. I have already a decent solution for this problem in my mind, so the update can be made public next Saturday at the latest. I apologize for the inconvenience.