Can't solve "Currency 'USD' not found" error
===

I'm getting this message at the frontend and the backend: There has been an error processing your request.

   When I delete the cache folders (var/cache, /tmp & /session) I get the frontend working again until I visit any page in the store with a price in it. The backend is harder to get working again (it isn't right now).

   Checking the error logs I get a whole bunch of them starting with "Currency 'USD' not found". This all started happening after a few minor changes including changing the order of the currency code from "$ 100.00" to "100,00 €" which I did by editing /lib/Zend/Locale/Data/es.xml (the spanish language specification) here:

      <currencyFormats>
        <currencyFormatLength>
         <currencyFormat>
            <pattern>Â¤Â #,##0.00</pattern>
         </currencyFormat>
       </currencyFormatLength>
       <unitPattern count="other">{0} {1}</unitPattern>
     </currencyFormats>

     I tried returning to the previous format and then copying the original file back. Something else must have broken somewhere and I can't find it.

     Here is a summary of the last steps in the Error logs (do you need them all?)

     a:5:{i:0;s:24:"Currency 'USD' not found";i:1;s:3740:"#0 /home/content/32/9343032/html/app/code/core/Mage/Core/Model/Locale.php(575): Zend_Currency->__construct('USD', Object (Zend_Locale))

#1 /home/content/32/9343032/html/app/code/core/Mage/Directory/Model/Currency.php(233): Mage_Core_Model_Locale->currency ('EUR')

#2 /home/content/32/9343032/html/app/code/core/Mage/Directory/Model/Currency.php(216): Mage_Directory_Model_Currency->formatTxt(NULL, Array)

#3 /home/content/32/9343032/html/app/code/core/Mage/Directory/Model/Currency.php(197): Mage_Directory_Model_Currency->formatPrecision(NULL, 2, Array, true, false)

#4 /home/content/32/9343032/html/app/code/core/Mage/Adminhtml/Block/Dashboard/Bar.php(82): Mage_Directory_Model_Currency->format(NULL)

Please help me out here...

Thanks
Miguel