it wouldn't be the stb or box that is bad, but either the cable or that hdcp handshake problem (which there aren't good work arounds for besides going component)
Keep in mind though there are a lot of people that get DVI and are still able to watch tv normally without a problem, so just because you see dvi, it doesn't neccessarily mean anything. If you're unable to watch tv because of it then, you'll want to reseat the hdmi cable first, see if your picture comes back, change hdmi ports on the tv, and see if it comes back. if it doesn't then you might be a perfect candidate to move over to component cables. the 1.7 upgrade fixed a number of hdmi issues for a lot of customers, but not 100% of them, so you can check with the AVS forums for your particular tv set to make sure there isn't a firmware upgrade that you should be taking advantage of, but other than that, you would have to wait for 1.8 to see if it corrects your issue. remember your manufacturer puts out similiar fixes too, so check with them as well.
