The issue that you are likely running into is that you are using Ripple's cross-domain proxy which is turned on in settings by default.
The cross-domain-proxy has 3 settings: "remote", "local" and "disabled". In my situation I actually had to disable it, but in some cases you would be able to use "local".
Possible scenarios:
1) your local application calls a remote service somewhere on another server:
you would either use "remote" or "disabled" depending on the configuration on the remote server.
2) your local application is on "localhost" and you are making a call to another localhost accessible URL:
you would either use "local" or "disabled" depending on your cross domain settings and such.
3) you are running a local app that calls a server that is also local but in a vm or something that makes it inaccessible to a proxy on "localhost":
you need to have it set to "disabled", and make sure your api server has settings to allow cross-domain requests. Most notably you would want to set the "Access-Control-Allow-Origin" header.