Ok I know I'm gonna sound like a newb with this but I'm just not sure wtf is going on.

I used to be able to load music from itunes to my iphone4 individually, Today I decided to just load my whole library. I changed the settings in itunes to sync entire library.

everything loaded fine, Then I decided to change that setting back so it doesn't try to auto sync every time. I plugged my phone in to download some ring tones I made and saw all my music is gone!

I tried to drag and drop into my phone and it wont work now. It does work with my old 3g though, What am I doing wrong here!