Song won't play on Iphone 4?

I have just bought a song off Itunes but it won't let me play or delete it how can I solve this.

It might not be with the compitable bitrate. Why do you download songs from itunes. What is the song you want. Don't pay for itunes. You can download almost any song for free.
Anyway do you have a media converter. If you have jet audio even you can do this. Just convert your mp3 to mp3 again. Sounds ridiculous? But just do it. Will work. I had the same problem with my ipod.