Apple released the new 3.0 Apple TV software update on October 30th. Yesterday Apple released an emergency update that Apple advises you to install immediately if you have already installed 3.0 on your Apple TV.
The new Apple TV version 3.0.1 prevents content from temporarily disappearing until it is resynced.
Apple has sent out email notifications to Apple TV users and also published this support page with more details.

The new Apple TV 3.0 features a redesigned main menu that supposedly makes navigating your favorite content simpler and faster, and makes enjoying the largest selection of on-demand HD movie rentals and purchases, HD TV shows, music and podcasts from the iTunes Store even better on your TV.
Buy an Apple TV on Amazon.com.