Windows 7 - Problem automatically syncing entire library in WMP

I have a sansa fuze and have been using it for a while with windows media player. Today after adding a new song, I plugged it in to sync and it automatically started REMOVING all my files. I stopped it, tried again and the same thing happened, so I just let it remove the files. When I tried to re-sync the library to my Fuze, it wouldn't. I click "start sync" and it takes a second, and says its done. Even though i formatted the device and have a library of 500+ songs. When I unplug it, the fuze is still empty. Not sure how to get it to sync the whole library automatically again. Help would be appreciated