If there are mutiple Messages that have the same translation, the routers array_search method will only match with the first message in the translation array. I fixed it by checking that both strings are equal message and translation.

 $translation = array
        (
            'Log out' => 'Abmelden',
            'Logout' => 'Abmelden', 
        );
$logoutRoute = new Zend_Controller_Router_Route
        (
            '@'._('User').'/@'._('Logout'),
            array
            (
                'module' => 'User',
                'controller' => 'Login',
                'action' => 'logout'
            )
        );

Example will allways use the default route because of matching route as "User/Log out" instead of "User/Logout".

===================================================================
--- Route.php   (Revision 23291)
+++ Route.php   (Arbeitskopie)
@@ -255,8 +255,11 @@
                         $part = substr($part, 1);
                     }
 
-                    if (($originalPathPart = array_search($pathPart, $translateMessages)) !== false) {
-                        $pathPart = $originalPathPart;
+                    foreach($translateMessages as $originalPathPart => $translated) {
+                        if($translated == $pathPart && $originalPathPart == $part ) {
+                            $pathPart = $originalPathPart;
+                            break;
+                        }
                     }
                 }