Cannot activate a license

When I make the call to activate, I get this message:

04-25 15:41:37.976: D/QlmLicense(1032): xmlResponse: <?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">soap:Bodysoap:Faultsoap:Codesoap:Valuesoap:Receiver/soap:Value/soap:Codesoap:Reason<soap:Text xml:lang="en">System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.Xml.XmlException: Data at the root level is invalid. Line 1, position 1.

Also, just for reference, here is the QlmLicense call:

private HttpResponse GetServiceResponse(final String _url, final String _licenseKey, final String _deviceId, final String _computerKey) 
                        throws ClientProtocolException, IOException 
{
    HttpResponse serviceResponse = null;

    HttpClient httpClient = new DefaultHttpClient();
    HttpContext localContext = new BasicHttpContext();
    HttpPost httpPost = new HttpPost(_url);
    List<NameValuePair> nvps = new ArrayList<NameValuePair>();

    nvps.add(new BasicNameValuePair("is_avkey", _licenseKey));
    if (isNullOrEmpty(_computerKey) == false) 
    {
        nvps.add(new BasicNameValuePair("is_pckey", _computerKey));
    }

    nvps.add(new BasicNameValuePair("is_pcid", _deviceId));


    httpPost.setEntity(new UrlEncodedFormEntity(nvps));
    serviceResponse = httpClient.execute(httpPost, localContext);

    return serviceResponse;
}

Any ideas?