Yup... im sure that this is the deal thats going on with yours.....http://forum.ecoustics.com/bbs/messages/2/180583.html
Notice the messages are different because you are using a different cable box, but BOTH messages tell you to use component. The way HDCP is supposed to work is that if it detects that you don't have rights to play an HD format (such as a bluray) then it will still let you watch the material but something near 1/4 of the quality of HD. Now for those of you who knows the EXACT specs of what it does when it keeps you from watching it in HD, no worries we aren't worried about the details lol.
If possible i'd check to see what firmware version of HDMI your TV and your Cable box are running on (if they are flash-able that is) some TV's allow you to update them over the internet. Your TV may be more up to date than the cable box. Either way, chances are its your cable box just as you see posted in the link above. Let me know what you find out, hope you get it resolved.