I have a 3806 (in a rack with other gear).
The 3806 turns itself ON, every day at 6:30am (it also turns off during operation, but this is random).
I tried covering the ir rcvr, no difference there.
btw, this is a replacement, the 1st one did the same thing

Check the power, I have heard of people haveing similar problems that are caused by power outages. Basically the power goes out, when it comes back on the receiver turns on. The power could be popping for just a second or two. You could plug it into a UPS and see if the problem goes away. These people wouldn't happen to have a generator that cycles on everyday do they?

I've since added a Panamax ups, but at 6:30 am every morning the 3806 turns ON!
btw, no generator at all

Here's a previous post:
[Link: remotecentral.com]

I had a similar problem with a Pioneer receiver about five years ago. The solution, when a replacement of the same model failed to solve the problem, was a change to a Marantz. My theory was that spurious IR or RF somehow activated the receiver, always at the same time. I reasoned that a different brand would have diferent IR or RF sensitivity. It worked.

I had a client whose ADCOM system would pop on and the volume would ramp up to full output late at night...

It was being triggered by a motion detector... When the cat would walk in the room, and trigger the motion, it would trun on the Adcom!

Was it a typical passive motion detector or an active one, maybe with microwave?

Most IR detectors are passive; the sense and area of IR, not emanate it.