It sounds like the cable box is having trouble getting an HDCP handshake because of the switching - common problem with devices that improperly implement HDCP. It's particularly odd, though, since you are also having to switch inputs on the TV. If you change the TV's input to the DVI/HDMI input after changing the 990's input to cable, try changing the TV's input first. A couple other questions: Can you turn the cable box off and back on and recover the signal? Do you have any other HDMI or DVI sources?