I read this in another thread and it worked for me:
Unplug AppleTV from power and HDMI. Plug it into your computer with only micro usb cable connected. iTunes will detect it.
Click on the Restore button on the main tab.
iTunes will download 4.4.1 from the net and install it on the ATV. After it finishes, plug the Apple TV back into your tv and you're good to go.
Shouldn't have to use a micro usb cable, but at least it works. Luckily I had one that came with my phone.