On several occasions, with both my 4s and IPAD2 (which are both set for wireless sync to my Macbook Pro), if the sync is interrupted, for example, I plug my phone in and then have to leave a few minutes later and take my phone, only some of the songs get synced. That is not unexpected. However, the only way to eventually get the other songs to sync back up is to hook the device up to the MBP, change the sync settings (ie tell it to sync only one specific artist or song rather than all my music), let it do that, then change it back to the entire library. What is stranger, when I plug in the device to the MBP, it shows all songs are set to sync, the sync process works, but the songs never make it to the device untilI do the trick above. Any advice?