Windows Media Center Channel Scan Finds all Channels but...

In my Media Center I have few of my favorite channels and its used to work great. But now some of my channels like 9.1 and 7.1 are not coming ? The same time, My TV had the same problem, I think the channel stop analog transmission, I am not sure why it affected digital transmission. I tried to do Channel scan on my all other TVs along with digital tuner and they started working I received all the channels. Now I am whenever I am trying to do anything with my Windows Vista Media Center, its search all the channels, but doesn't receive the transmission for Channel 7 and 9. Can you please how I can fix this issues ? Your help will be greatly appreciated.