Sandisk Sansa View with Windows Media Player - claims it's full when it's not?

I have an 8GB Sandisk Sansa View mp3 player, and Windows Media Player is set up to sync my music. The other night, I had 3.5GB left, and then this morning WMP says it is full. Now, the internal memory of this model is roughly 7.5 according to the specs, but since there was nothing new added, and the actual player data (accessed from the main menu and system settings) confirms that there is nothing new added, as well as 3.5GB left to fill. Does anyone know what caused this, and how I can fix it? It won't auto-sync anymore, so I have to track down every single new file I want to add, even though WMP starts up to sit there and say it's full (which, once again, is confirmed not to be). Kind of annoying, but livable if no one has a reason. Thanks~