I see this issue catch a lot of people, and it got me today. If you have a file /api/test.cfm on ColdFusion 10 or greater it might not work due to ColdFusion's REST implementation controlling the /api or /rest URIs. You will get a empty response, the only clue is a http response header that says: server-error: true
The irony is that I remember telling Adobe in pre-release that this will catch people off guard, I suggested that they should pick a URI that is not so commonly used. I understand why they kept it, but it causes some havoc every now and then.