what does it mean when it says "waiting for changes to be applied" before it will sync my iphone to my music library?

I am trying to delelte some songs that went onto my iphone. The songs are ones my daughter had in the itunes music library. I unchecked all the ones I didn't want on my iphone. Now I'm trying to sync my iphone with my itunes music library and it keeps stopping at step 2 and says "waiting for changes to be applied" and the syncing just stops.