Itunes 11.1.4 isn't syncing properly to my Iphone 4S

I have an Iphone 4s and recently downloaded Itunes 11.1.4 to my PC. At first it wouldn't recognize my device, and I reinstalled the drivers and everything, but it still wont sync properly. It starts the sync and then gets up to step 6 of 6 to wait for changes to apply, but then the sync just stops. In addition to this, it did something to my music on my phone. It deleted many of the songs, or made them unplayable (they're in gray lettering and aren't able to be selected. plus there is a red circle with a square in the middle next to each song.) I've tried uninstalling Itunes and then reinstalling it again, but I keep having the same problem. I don't know what else to do and I'm really frustrated that I can't sync my phone to my computer.