You seem to have mentioned two separate issues so far. One is, when you turn on the Denon to listen to CD or radio, it turns on the Samsung TV as well, the other is, when you turned the TV off, you get "sound blanks out on the Denon after about 30 seconds.
Have you done the following, that have been mentioned in previous posts?
1. Denon: Set HDMI control to "OFF".
2. Samsung TV: Turn Anynet, HDMI+CEC, or anything like that, "OFF".
If even with the above done, the Denon is still turning off the TV and/or vice versa then it would become to sound like a compatibility bug, that may be affecting those two models. My Sony XBR900e/Denon AVR-X4400H have only one apparent bug that if I turn the sony TV off, it would mute the Denon AVR, but muting is just a minor nuisance, and by turning off Sony's Bravia sync, or even just the Bravia sync's powering on/off feature fixed it, so strictly speaking it's not even a bug.