Thank you for your help, but no, a power off/restart does nothing to fix this.
Turn the Arc on, turn the wifi on, open browser from home screen and get a "webpage not available" In other words, the browser does not appear to recognise that the tablet is connected. Open email app and get "Couldn't open connection to server", again, it appears the app doesn't recognise there is a wireless connection.
It appears to be a setting that has been disrupted so that apps don't recognise the wifi connection. Very frustrating.