Music won't play

[sjschenk]

I have noticed that ever since the Pre was able to sync with iTunes that certain music will not play. Most of it is music that I have purchased thru iTunes. And it seems that most of them are the Alternative rock that I bought. for some reason the songs that I downloaded from a friend work just fine, but purchased songs don't. Is there perhaps a type of parental control on the music player as default? Thats the only thing I can think of because most of the songs are Linkin Park, Blink 182 etc.