FileNotFoundException on Android 版本 > 2.3

我尝试将文件下载到手机上的SD卡。在Android 2.1，2.2和2.3上，一切都按预期工作，但在Android 4.0（模拟器和我的Galaxy Nexus上测试）上，它会抛出一个.FileNotFoundException

堆栈跟踪：

02-27 21:49:06.733: W/System.err(27648): java.io.FileNotFoundException: http://www.wdr.de/wdrlive/media/wdr5.m3u
02-27 21:49:06.733: W/System.err(27648):    at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:177)
02-27 21:49:06.733: W/System.err(27648):    at de.arvidg.test.StartActivity$9.run(StartActivity.java:833)
02-27 21:49:06.733: W/System.err(27648):    at java.lang.Thread.run(Thread.java:856)

我的文件下载方法：

downloadFile("http://www.wdr.de/wdrlive/media/wdr5.m3u");

    public void downloadFile(final String fileUrl) {
        new Thread(new Runnable() {

            @Override
            public void run() {
                try {

                    URL url = new URL(fileUrl);

                    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

                    urlConnection.setRequestMethod("GET");
                    urlConnection.setDoOutput(true);

                    urlConnection.connect();

//                  File cacheDir = appContext.getExternalCacheDir();
//                  File file = new File("/mnt/sdcard", "/cacheFile.ext");
                    File SDCardRoot = Environment.getExternalStorageDirectory();
                    File file = new File(SDCardRoot,"/cacheFile.ext");

                    if(!file.exists()) file.createNewFile();

                    FileOutputStream fileOutput = new FileOutputStream(file);

                    InputStream inputStream = urlConnection.getInputStream();

                    int totalSize = urlConnection.getContentLength();
                    int downloadedSize = 0;

                    byte[] buffer = new byte[1024];
                    int bufferLength = 0;

                    while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
                        fileOutput.write(buffer, 0, bufferLength);
                        downloadedSize += bufferLength;
                        Log.d(TAG, "downloadedSize = " + downloadedSize + " | totalSize = " + totalSize);
//                      updateProgress(downloadedSize, totalSize);

                    }
                    fileOutput.close();

            } catch (MalformedURLException e) {
                    e.printStackTrace();
            } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        }).start();
    }