Mine, too. I have two Airport routers. Things were working great for a little over a month. Then the Chromecast disappeared. After a thousand reboots and reconfigurations, here's what fixed it: set the channel on the 2.4GHz network. It instantly reappeared on all my devices. Chromecast engineers: die in a fire.
Photograph: Andy Loghin [via thisnewurbanity.]