Achievement API

Getting a "page not found" error trying to show the details for specific Achievement ID using the Achievement API. This was working last week. To rule out my own error, I followed the link in the API Documentation, but get the same error.

Using th URL of http://us.battle.net/api/wow/achievement/2144
results in: {"status":"nok", "reason": "When in doubt, blow it up. (page not found)"}
Thanks!