@nukenuky, since you said you live in Vietnam I am anxious to see what I can do to help. So I tried to duplicate your problem and to see if i can fix it for you without you have to send the Onkyo to a service center.
I do have good news for you.
I did duplicate your problem , got the no signal and everything froze and have come close to bricking my own 809.
1. You need to remove your Onkyo usb wifi dongle. I had the same problem with my usb dongle.
2. Unplug the power plug, wait for 10 minute.
3. Plug in power plug
4. Put your usb flash drive with the 3 files from the zip file downloaded from Onkyo
5. press usb on the remote until it recognizes your usb drive. Mine was a Kingston drive. This is important. If you click on the drive, it will say nothing.
6. Go to Hardware setup, Network. There should be nothing in it.
7. Go to Hardware setup, Firmware update, choose usb and update. It will choose the usb drive recognized earlier automatically. Otherwise it will not work.
8. You should see the downloading and writing of the files to your TV.
9. Completed and you are done.
10. Re-install the usb dongle.
Remember, you need to use the front panel ON/OFF switch not the remote on/off switch. When you got the no signal and initializing then you need to unplug the power plug. When I duplicated your problem I thought it was exactly the way you described it and my Onkyo was bricked.
Let me know how you make out.
The above procedure is for those of us who use usb wifi dongle which causes a problem for the Onkyo when usb is used to upgrade. i would suspect that if you have a wired ethernet then, you will not have the usb problem.Edited by chanc - 6/14/13 at 3:59pm