Anjali and I had a problem similar to this at our apartment. Some channels came in great, some awful. But we called the cable company and they fixed the wall jack, which was apparently old and falling apart, and things work much better now. And our internet works much more consistently (which was actually our main reason for calling. We got by with the fuzzy TV stations but couldn't live with internet not working).
Try simply changing the TV cable - worked great for me 
Commenting by HaloScan
