I have same problem with box on Charter. Had DCT 3416 that worked fine with TV for about 6 weeks. Then, for no discernible reason, it lost video, locked up, and put a "dui" (which is actually DVI) on the screen. I got a new box, a DCH3416 and after they provisioned the box, it too had the same error. I am convinced it is a firmware error. I believe (but haven't confirmed yet) that they must have upgraded the soft/firmware in the past week or so here in St. Louis and, as a result, the HDCP errors are now occurring. I don't see a solution at the moment unless they change the firm/software that would fix the incompatibility or handshake issue.
In the meantime, all the analog outputs work including component so at least for awhile, I will watch this slightly degraded picture. If they can't fix it, I will probably give satellite a try since they are offering me $350 to sign up for a year and they have more HD available than Charter...at least at the moment.