Currently Being ModeratedNov 7, 2012 8:30 AM (in response to c4miles)
Under settings you can restore ATV to factory settings. You will have to go in and re-enter all your passwords sent settings, and the version it will revert to will probably not work with iOS6.
Currently Being ModeratedNov 7, 2012 8:56 AM (in response to Brian Cook4)
Thanks for the tip. I had not tried that because the Apple documentation says (quote)
Restoring your Apple TV (2nd and 3rd generation) to factory settings
On Apple TV, choose Settings > General > Reset, and then click Restore.
Your Apple TV will restore to its factory settings, and will also download and install the latest Apple TV software update. This process may take some time. Do not disconnect your Apple TV's power cable during the restore process.
If you cannot use this process, and you have a micro USB cable, try the steps in the next section.
(endquote) and I do not want "the latest Apple software".
In the meantime I've solved the Apple TV problem by udating my mac mini to OS X 10.8 and agreeing to T&Cs. Then PhotoStream appears on Apple TV. I'm steering clear of iOS 6 as no iPad 1 support (seriously ****** off).