This is happening only when I save, for a store view, the Romanian locale. On this shop, the allowed currencies are US$, Romanian Leu and EURO. I set Currency Rates for each allowed currency: if US$ is default currency then I have a specific currency rate, if Romanian Leu is default currency another specific currency rate and exactly the same thing for EURO.
I searched on google about this error but the only solution that I founded was to clear var/cache and var/session ... Well, that isn't a solution.
a:5:{i:0;s:24:"Currency 'USD' not found";i:1;s:5065:"#0 /app/code/core/Mage/Core/Model/Locale.php(576): Zend_Currency->__construct('USD', Object(Zend_Locale))
/app/code/core/Mage/Directory/Model/Currency.php(233): Mage_Core_Model_Locale->currency('RON')
/app/code/core/Mage/Directory/Model/Currency.php(238): Mage_Directory_Model_Currency->formatTxt(0)
/app/code/core/Mage/Core/Model/Locale.php(682): Mage_Directory_Model_Currency->getOutputFormat()
/app/code/core/Mage/Catalog/Block/Product/View.php(168): Mage_Core_Model_Locale->getJsPriceFormat()
/app/design/frontend/magento-boilerplate/default/template/catalog/product/view.phtml(69): Mage_Catalog_Block_Product_View->getJsonConfig()
/app/code/core/Mage/Core/Block/Template.php(241): include('/home/mediaswit...')
/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/magent...')
/app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
/app/code/core/Mage/Core/Block/Abstract.php(863): Mage_Core_Block_Template->_toHtml()
/app/code/core/Mage/Core/Block/Text/List.php(43): Mage_Core_Block_Abstract->toHtml()
/app/code/core/Mage/Core/Block/Abstract.php(863): Mage_Core_Block_Text_List->_toHtml()
/app/code/core/Mage/Core/Block/Abstract.php(582): Mage_Core_Block_Abstract->toHtml()
/app/code/core/Mage/Core/Block/Abstract.php(526): Mage_Core_Block_Abstract->_getChildHtml('content', true)
/app/design/frontend/magento-boilerplate/default/template/page/2columns-right.phtml(51): Mage_Core_Block_Abstract->getChildHtml('content')
/app/code/core/Mage/Core/Block/Template.php(241): include('/home/mediaswit...')
/app/code/core/Mage/Core/Block/Template.php(272): Mage_Core_Block_Template->fetchView('frontend/magent...')
app/code/core/Mage/Core/Block/Template.php(286): Mage_Core_Block_Template->renderView()
/app/code/core/Mage/Core/Block/Abstract.php(863): Mage_Core_Block_Template->_toHtml()
/app/code/core/Mage/Core/Model/Layout.php(555): Mage_Core_Block_Abstract->toHtml()
/app/code/core/Mage/Core/Controller/Varien/Action.php(390): Mage_Core_Model_Layout->getOutput()
/app/code/core/Mage/Cms/Helper/Page.php(137): Mage_Core_Controller_Varien_Action->renderLayout()
/app/code/core/Mage/Cms/Helper/Page.php(52): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'no-route')
/app/code/core/Mage/Cms/controllers/IndexController.php(75): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'no-route')
/app/code/core/Mage/Core/Controller/Varien/Action.php(419): Mage_Cms_IndexController->noRouteAction()
/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action->dispatch('noRoute')
/app/code/core/Mage/Core/Controller/Varien/Front.php(176): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
/app/Mage.php(683): Mage_Core_Model_App->run(Array)
/index.php(87): Mage::run('', 'store')
Please help. Thank you.