Comment 13 for bug 746694

The LANG environment variable must have a valid locale name, or else many i18n things are screwed up.

To users, who have chosen to receive backports updates, a surprising security update resulted effectively in a (temporary) downgrade with respect to the language related stuff in the backports gdm package, since the backports package was suddenly not the latest gdm version. That's what caused the invalid LANG value.

To clean it up, once you have installed version 2.30.2.is.2.30.0-0ubuntu5.1+langfixes~lucid1 or 2.30.5-0ubuntu4.1+langfixes~maverick1, following these steps should suffice:

* Open Language Support
  System -> Administration -> Language Support

* Select the "Regional Formats" tab

* Change the setting one or more times

* Log out and log in again

I don't know anything about the weather applet, though. Maybe, for the case you have never set the temperature unit explicitly, there is a default which is affected by one of the LC_* variables. ;-)