The session/desktop name (displayed in the title of the client) does not properly handle if the system is not running UTF-8. ASCII works fine, but antyhing else is assumed to be ISO 8859-1 (for legacy reason). If the local coding doesn't match ISO 8859-1, then the wrong character will be displayed.
As an example, the € sign in ISO 8859-15 will be displayed as ¤ instead.
Happens both with the desktop name specified on the command line, as well as when specified via vncconfig.