Motorola. DCH 3200 rebooting

First thing that comes to mind is bad signal on the upstream. Think of the cable like a 2 way street, the signal coming in gives you the picture, the signal going out is for the guide, the OD and how the box connects to Cox to know what channels you get. If it can't connect to Cox to get that information, it keeps rebooting trying to activate. 

But when you say "dark" do you mean the box won't power up at all? If so, thats more likly a power problem if it effected multiple boxes. If you just mean no picture, then can you describe how it reboots? Like what it says on the display and/or screen.

Thanks for the reply.

This box, would start to reboot after watching about 30 min of tv. The screen on tv would go green then the box would go black, and a word that looks like "dui" would pop up, followed by something like 8888, then the tv would come back on as it said standby loading. It was doing this every 10 minutes and finally on the last reboot, the cable box just went black after the DUI popped up. It doesnt work at all anymore. Tried unplugging it. everything.

The problem is this. I had a different box from cox for 2 years. Never had this problem. (All at my current location). then 2 months ago, the old box started rebooting constantly. Had a tech come out, he said the box was bad, and gave me this one. This started doing the same thing almost immediately. Left town for three weeks, and when I got back, same problem. Did not even get one night out of this POS

Well if its the same symptom with both boxes, probably not the box at all. Even if both boxes were broken, the likelihood of them being broken in the same way is pretty slim. The DUI (as funny as it would be if the box was just drunk) actually is the boxes way of saying DVI (Digital Video Input). Usually happens when there is a HDCP (High Def Copywrite protection) issue. HDCP is the encryption used by HDMI, the wire you probably use to connect the box to the TV. If it fails, the box resets so it can try to re-sync with the TV. Another tip its a HDCP issue is the green screen, thats a dead give away.

So first try a new HDMI cord. If that doesn't work, try turning the video output to native and set your TV's aspect ratio to just scan, or what ever the equivalent is. We might need to play around with those options, but first try a new HDMI, and make sure its version 1.4, but don't buy anything expensive. 20$ at walmart will be fine, or you can try http://www.monoprice.com/

A simplier, cheaper alternative would be to use component wire instead. You can get these free at any Cox store or can be bought from any walmart. In a pinch, you can even use two sets of composite(red,white yellow cord) instead. To the expert eye, you will see a drop in picture quality with component over HDMI, but if nothing else its a good temporary work around.