Ok a few things. What cable box do you have, you say modem which is not correct. If you plug the cable wire directly into the tv do you have a picture? Are you new to the system. have you just transitioned from the old guide to the new iguide on your cisco or scientific atlanta box? More info is necessary before anyone can even begin to assist you.
One day I had a picture and the next day I didn't. I just get horizontal lines and the #99 in top right corner, They told me to reboot the modem, wait 10 minutes and turn on the tv. I've now taken it off hd and plugged the cable into the tv. Other than getting the guide, I wonder why I'm paying extra! Any suggestions.?