Here is how you can fix your YouTube App on your AppleTV2, via ATV Flash (Black) 2.6 which is Created by FireCore
Here is what you need to know first:
1. Tell Difference Which AppleTV your Holding ( AppleTV 2 or The New AppleTV 3)
http://goo.gl/F5qXtx
2. Download Seas0nPass
http://goo.gl/KhcPE4
3. Install XBMC and nitoTV via Nito Installer
http://goo.gl/JzQgpR
4. Install aTV Flash (Black) 2.6 – AppleTV2
http://goo.gl/zAynjI