I have read about this problem. What you need to do is to update your phone software. Read the instructions about N Series here
http://www.nokia-asia.com/nokia/0,,96205,00.html#21
When you will connect to Nokia's website, it will tell you that you have latest software and then ask you whether you want to reinstall. You say "Yes" and then it will download approximately 45MB of software. It will install this software on your phone...restart the phone and voilla...you have the green theme and the music button working as expected.
Remember, this is what I have read on net somewhere. I do not remember which site because I recently read so many websites about mobile phones that I don't remember
