It took me almost a week but I finally figured out how to downgrade from any firmware to a previous firmware that is no longer being signed by Apple. This is for those of us that purchased an apple tv 2 that came with a version of iOS newer than 4.3. Thus, no SHSH blobs are available for the downgrade.
In my case, I needed to downgrade from 4.4.4 to 4.3 on an Apple tv 2 that my friend purchased about a week ago.
These are detailed instructions. If you have trouble, start over from the top.
Find your “hosts” file on your computer.
For a mac, it will be in /etc/hosts. **NOTE: You may need to change your mac settings so that you can view hidden files and folders.
To do this, open up your terminal and type: “defaults write com.apple.finder AppleShowAllFiles TRUE” without the quotes and hit enter. Open up finder and you should now see all of your hidden files. To turn this off, re-type the same line in terminal but change TRUE to FALSE.
For a pc, your hosts file will be in c:\windows\system32\drivers\etc\hosts
Open your hosts file in a text editor and add the following line to the very bottom of the hosts file:
Connect your apple tv 2 to your computer. If iTunes opens, close it.
Open Seas0nPass and follow the instructions here http://support.firecore.com/entries/387605-jailbreaking-101-seas0npass to do the untethered 4.3 jailbreak.
That’s it. Very easy and straightforward. Once Seas0nPass is done doing the jailbreak, disconnect your apple tv 2 and proceed to do whatever you need to do with it (i.e. install xbmc and icefilms).
The line that you added to your hosts file will block apple from verifying the IOS firmware. Remember to go back in to your hosts file and remove the line you added so that iTunes can update like normal again.
I’ll try to keep an eye on this thread in case anyone has questions.