The Tech Supervisor just left. He was baffled while my TV worked fine on most channels using HDMI, but others did not.
Changed inputs, changed cables etc., and still the same problem. Was going to try a new Genie box, when I remembered I had an old HDMI splitter laying around.
Hooked the HDMI cable from the Genie to the splitter, and then HDMI cable out of the splitter into my TV. Viola! Works fine now on my problem channels. Don't know why this works, as I think the splitter I had was older than my TV, but if anyone else has this problem, give it a try. Much better solution than having to use component.