I'm running Android 4.2.2 on a Galaxy Nexus with the February 13, 2013 update of Google Search installed. Google Now was working great until it suddenly ceased to appear today. Widgets now display "Get Google Now", and the Google Now screen itself only contains a search box, not even showing the Google Now-related items that were in the settings menu previously.
I rebooted the phone multiple times and upgraded all apps, but the problem has persisted for the last few hours. What gives, and is there a way to "reset" Google Now?