How to stop Setup Assistant from showing up on every restart on Mac Mini with OS X Mavericks?

My Mac Mini is new. I'm not sure if this issue was already there before installing Server.app. Unsusual things happen with the system on EVERY RESTART: Messages Agent ask permission to use keychain to which I say "always allow" and it pops up again till I say only "allow"; Dock gets resete (all customization lost); it always notifies me that I can download iwork for free but I already did; it always asks for icloud password. It´s like it resets some stuff every startup.