UPDATE: a more useful replacement for currency translation can be found here: https://blog.philwinkle.com/webservicex-is-down-i-have-a-fix/
I thought this issue was worth raising as it is affecting a lot of stores selling in multiple currencies. The problem is that the WebserviceX service is failing more often than it works meaning that many stores have out dated currency conversions for products they will in multiple currencies. If you are running this via a cron job you may miss this all together till you sell something for less then you actually paid for it.
If you run this manually (System > Manage Currencies > Import) you will see:
Problem : Cannot retrieve rate from http://www.webservicex.net/CurrencyConvertor.asmx
Solution… Magento community to the rescue..
You can see from this post here there is a small patch supplied by user SnufPunK. This patch can be accessed from here. This will install a new Webservicex.php which uses the new google converter in app/code/local/Mage/Directory/Model/Currency/Import/ and edit app/code/core/Mage/Directory/etc/config.xml so that currencies are imported every 30 mins (adjust as you like).
This works fine in Magento 1.7x / 1.8