I never did find a thread on this topic in the past, so I’ll post this in case someone else is experiencing this issue.
My ATV2 does not ever go to sleep. I can’t even get it to turn off. Around the time this started occurring (Christmas Time), I got a Harmony One. Roughly around that same time there were also upgrades to Media Player and Maintenance. So I cannot pinpoint the source of the issue.
Happy to report today, after applying aTV Flash (black) release 1.3 (including functionality for Harmony) as well as an Upgrade to Maintenance, my ATV2 is now sound asleep. It powers off when my Harmony One tells it to. I haven’t actually checked if it goes to sleep on it’s own after the pre-set period of inactivity.