davesnake has been testing 2.16a, which fixes this issue.
This problem occurs on hosts where Apache is configured not to listen on the localhost interface.
Here's an excerpt from the changelog:
Improvements in Release 2.16aPlease upgrade to 2.16a (attached) if you see this error.
New option added: do_check_url option, default false
This checks to ensure that the requested URI/L exists before sending it to the translator.
When true, it can reduce load on the translation servers by preventing the attempted translation of URLs which do not exist.
This must be set to false if your server cannot talk to itself.
The check_url_proxy variable is the host which the script will use to check URLs. The default is 'localhost:80'.