I had this too. I just upgraded to 3.5 - for 3.2 the other night. After the 3.5 upgrade was completed - everything was great. My external HDD was still available - and all of the editing of the OS files I had done to remove unwanted menu items remained just as they were. Perfect!
So - start watching a cartoon with my daughter - and she wanted me to rewind a funny part - which we always do - and boom - black screen and the Apple TV restarts.
I use ATVFiles for all movie watching - i never use Nito at all and did not try it to see if it would work.
So - we go back to the cartoon - and manually get back to the spot by FF - and then she wants me to rewind. boom. machine restarts again.
Now - that was a few days ago - and i don’t remember the cartoon - but I have since been able to rewind my movies and it has been fine.
If it comes up again - i will try Nito to see if that makes a difference.