On my TIKI (1.9.0), when a users has a non-English language preferene, some of the links on the page do not work — they result in blank pages.
For example, when using English interface, the LOGOUT link works fine — users are logged off and the home page appears. However, when using French (or Spanish, etc.), using the LOGOUT link displays a blank screen. I checkec the logs and the user is being logged out properly, but the home page (tiki-index.php) doesn't appear.