I have found that those particular HDMI "features" can be flaky depending on the components.

My GF has an Onkyo TX-SR33. It will work fine for a while, and then every once in a while (every couple weeks), the HDMI-CEC features will stop working. By this I mean: Turning on a device won't turn on the TV and switch to the correct input on the Onkyo, I must pick up its remote and turn on the TV and switch it to the correct input.

When the CEC features stop working, the only thing that will get them functioning again is a power cycle of the Onkyo. And I don't mean "pick up its remote and turn it on and off again", that doesn't work, because the on/off on that thing is actually just a "standby". No, I mean that I must physically unplug the thing to get it to fully reboot. Then the CEC features work again for another week or two.

I have another Onkyo at home in the living room, a TX-NR686, that I haven't had any trouble with, but I must admit that I haven't used its CEC features because I'm using a Harmony remote in that location and I don't need those features.

I interpret this as: Embedded firmware for complex systems is hard to make reliable. We looked for firmware updates for the flaky model a while back, but there weren't any. I should check again some time.