It sounds like you're getting some kind of "handshake" issue between the receiver and the TV. Try connecting the HDMI-DVI cable from your cable box directly to your TV. Do you get picture then? If so, I'd say hook up your TV that way, and then use an optical cable from the cable box to the receiver for your sound. You can also use RCA cables to your TV for sound from your TV.
I had my old Mitsubishi TV hooked up that way.