When the function isLocale is called from within the Translate view helper it will evaluate an integer 0 to a locale thus causing the vsprintf to fail when utilizing this to be sent for evaluation.

This broke BC between 1.6.2 and 1.7.

Reproduction: in a view script $this->translate('something %s', 0); which will now throw an exception because 0 became a locale due to the Zend_Locale::isLocale handling. This might be more of a bug in the Zend_View_Helper_Translate more than anything. Please see the view helper fix below.

Likely in the view helper itself, it should call strict since it is evaluating the result (patch):

 
Index: libraries/Zend/View/Helper/Translate.php
===================================================================
--- libraries/Zend/View/Helper/Translate.php    (revision 12678)
+++ libraries/Zend/View/Helper/Translate.php    (working copy)
@@ -82,7 +82,7 @@
         $count  = count($options);
         $locale = null;
         if ($count > 0) {
-            if (Zend_Locale::isLocale($options[($count - 1)], null, false) !== false) {
+            if (Zend_Locale::isLocale($options[($count - 1)], true, false) !== false) {
                 $locale = array_pop($options);
             }
         }