makeWebRequest responseCode returns -400 on device, but works in sim

Hi,

I am trying to get a JSON request from the following site: http://api.holfuy.com/live/?s=101&pw=pass&m=JSON&tu=C&su=m/s  (example URL you can use for testing).

Here is the api description: http://api.holfuy.com/live/

My code looks like this.

function makeRequest() {
       var url = "http://api.holfuy.com/live/";                         // set the url


       var params = {                                              // set the parameters
              "s" => "963",
              "pw" => "************",
              "m" => "JSON",
              "tu" => "C",
              "su" => "km/h"
       };

       var options = {                                             // set the options
           :method => Communications.HTTP_REQUEST_METHOD_GET,      // set HTTP method
           :headers => {                                           // set headers
                   "Content-Type" => Communications.REQUEST_CONTENT_TYPE_URL_ENCODED},
                                                                   // set response type
           :responseType => Communications.HTTP_RESPONSE_CONTENT_TYPE_JSON
       };

       var responseCallback = method(:onReceive);                  // set responseCallback to
                                                                   // onReceive() method
       // Make the Communications.makeWebRequest() call
       Communications.makeWebRequest(url, params, options, method(:onReceive));
       }

Everything works perfectly on the sim, but on my device (Tactix delta with v9) I receive the -400 error.
I don't know a lot about JSON, therefore trouble shooting hasn't gotten me anywhere yet.

I checked the data that comes back from the server. From what I can tell it looks like a proper JSON object, so from my understanding it should work.

Does anyone see what I am overlooking?

Any help would be really appreciated

best regards