I tried doing the same thing that had been advised to do on the Play/pause pandora.com with a media key answer page. I simply replaced the XXX with 119 after running GetMediaKey - instead of 122 (it was same for me), which worked just fine for its play/pause purpose. I also replaced the YY with 11 since it was the appropriate (and next) tab.

It does put the small, orange, dotted square around the next song button, but instead of going to the next song, it just acts like play/pause. Is there another modification required?

Using Google Chrome in Windows 7 on an Alienware m14x r2.