I am curious if it's an compatibility issue. The reason I am curious because i have that same problem from day one (I am with TWC). I never press the issue because the component connection was good enough for me, but that really would be a problem if the TV only have hdmi.
Over the past couple of years I have had problems hooking up any HD plasma tv with HDMI to the Comcast cable box - seems like a simple thing to do - plug in my expensive HDMI cable into the Comcast cable box and then plug the other end into the tv. Sometimes it works and sometimes it doesn't. After years of this "works for a while and then it stops" - or multiple cable boxes from Comcast that don't work... today the technician who came to my home said - "there is a problem with the boxes and not all of them work right" - how can this be? Is it true??? So many of them?? I can't go into all the combinations of boxes and tvs I've tried but right now I have a 32 inch Samsung hooked up with component cables to a DCT3416 1 Motorola box because the HDMI connection from the box does not work (an HDMI DVD player does work with the tv however) and a cable connection from a Motorola cable box without an HDMI hookup (because the technician didn't realize I wanted one) to a 42 inch Panasonic. They will bring me two more boxes with HDMI next week to try again.