Can't play a certain song on my Iphone

I just download a song of the internet (legally) and its on itunes. I played it on itunes and it works. I synced it on my iphone 4 and it's on there, but the song is highlighted gray and it won't let me click on it or play it. Why? I have other songs i downloaded and they work. The song is 7 MB.

Does it cost to text from USA to puerto rico?

Well my friend moved down there and we wanted to know if it was costing anything. I have unlimited texting, but not unlimited picture messaging? But i have AT&T & an iPhone 4. He has iphone 3, he doesn't have at&t, he has 'claro' which is verizon in puerto rico, but a mexican group bought it. He has unlimited texting.

My IPhone 4S will not receive any images?

I have the iPhone 4s and I'm not able to receive any images. I can send them but I will not receive them. I have my MMS on and my Cellular Data. I have 1 GB left in storage and I can't figure out why I'm not able to receive pictures. Is anyone able to help?

Iphone 4 vs Nokia lumia 900?

What should i Get an iphone 4g or an Nokia Lumia 900 i heard people saying Iphone 4g is more better than nokia so what should i get? I need your guys help!

Is the personal hotspot option on the iphone safe?

I just learned i can use my iphone as a hotpot and i freaked out! Apparently you go settings, general, network, the it says personal hotspot! So is it safe? More importantly does it cost a lot or free?

My iphone ran out of battery and now it won't turn on?

My Iphone ran out of battery meanwhile i was using it so then i go ahead and charge it i come back 10-20mins. And it wouldnt turn on for some reason so then i tried another charger for the somae amount of time but still nothing it wouldnt turn on so i tried a third charger and i charged it for about a hour and still nothing no picture or anything like its all lifeless i tried holding the power button, but still nothing, i already tried resetting it and all and i also already tried connecting to iTunes in recovering mode can someone please help me i have some really important stuff in it so can someone fix it without resseting all the settings
iPhone 4, iOS 5.1.1