Indeed a severe annoyance. I spent a lot of time on the phone to Apple and no solution was achieved, only "wait". I ended up doing a simultaneous reinstallation of OS X 10.10.3 and my iOS 8 devices and this has apparently made them go away. I have since upgraded to OS X 10.11 and iOS 9 and they disappeared for several months. However, they have notjust come back this AM for no apparent reason on startup.