Apple TV 3 and network time problem (after Update to 5.1!?) My Apple TV (3rd generation) doesn't connect to the internet any more because it doesn't succeed in getting the network time from my router.

I tried restarting, updating, resetting both – the Apple TV and my WLAN router (TP-Link 1043ND), I double checked the network time in my router, tried out an alternative firmware (DD-WRT), put down all security settings (no password), tried direct connection per cable (LAN) on Apple TV – but nothing worked:

I always get the screen that Apple TV tries to fetch the network time (I'm in Germany) – the manual selection of Berlin as time zone doesn't help.

It all worked a few weeks ago – after an update of the Apple TV Software it all went away ... my Apple TV got useless because it needs the correct time settings to connect to the internet.

Does anyone have an idea what I can do?
My TP-Link router had problems with AppleTV. The iPad didn't see Airplay. I resolved it by following this Apple KB page on iOS and OS X: Recommended settings for Wi-Fi routers and access points.