when I say power cycle I mean pull the plug from the wall.
This is the notes I have for what I did to resolve the issue.
10/23/2011 6:21pm turned on denon from zone2 radio and .net as was testing remote. turned on and then off and then on and off again. noticed that I was getting no response on my management page http://192.168.0.47
nor could I telnet to 192.168.0.47 on port 80. Interestingly I could ping 192.168.0.47.
so i go downstairs to investigate. 6:28 I cycle the power on zone2 using the remote one more time, turn it back on and again the web interface is not responding, I can ping but can't reach the interface. 6:32pm next i power off the receiver by pulling the power plug pretty sure zone2 was still on. I believe it was powered on with zone2 still active. still no network anyway I hit the standby button on the front to power down and power it back on. This time its 6:36pm still no network, so I power off the receiver. check connection cables in rack, find some lose ones in the switch, tighten then up and come back to theater room. execute on command from remote to turn on projector and power on the receivers main zone, this time it is 1/23/2011 6:40pm . next I browse to the networking status, entire receiver freezes up and is frozen. I am forced to pull the power to the reciever from the power cord. at this point while in the back of the unit I go back to the cabinet and re-examine network switch and cables thinking maybe on my first config i made it worse. 648PM Now I power back on receiver 6, I can see networking status, firmware update avaiable again and can connect to the web management page. its back now, At 735pm decide its a good idea to power back on the receiver to see if any options to configure zone2 output, etc. around 750 update the firmware after the quirkiness with the network card. the upgrade lasts from 753pm to 813pm. and havent had issue since.
so the question is, was physically pulling the plug while the receiver was locked up/turned on the thing that fixed it? its a risky call but what do you have to lose at this point? You could try pulling the plug with your receiver on. then once you plug it back in the receiver will power back on, push the little black button to power it back down and push it in again to power it back.
other thing too is try starting up the receiver with network standby on, see if simply changing from network standby off to on is enough to refresh the network configuration and make it boot.