iTunes won't launch after purchasing some new songs. I bought songs, one song became interrupted, re-downloaded it, song would not play, closed iTunes, tried reopening, iTunes unresponsive, help please!

I recently bought some new songs and one song during the download process was interrupted, i didn't think much of it, i figured i could just re-download it. today i opened up iTunes and didn't see it in my library. I went to the iTunes store, went to purchases and saw the song was purchased, but not downloaded into my library. I downloaded it and when it was done, i went to my library to play the song. It was unresponsive, no sound, no playback, no song. I decided to make an AAC copy of the song to atleast have a functioning version. still not working, tried playing other songs, iTunes unresponsive, closed down iTunes and tried to relaunch. iTunes won't open. I tried doing the trouble shooting displayed on the "support" section of the Apple website but no luck. please help, i basically have nearly $1000 worth of merchandise in my iTunes library and i'm not able to access any of it.