TiVo HD or S3?
I didn't have the exact same problem, but I had a similar problem when I first got my S3 up and running. Certain channels (all of the local HDs) were blocked--signal strength 0. One CSR actually tried to tell me that local HD channels were not a part of my package! It took several escalating calls to Comcast. I eventually called the 'executive assistant' which someone recommended to me on this forum (215-665-1700). The Executive Assistant sent out a competent tech who had the problem fixed in 5 minutes.
I didn't have the exact same problem, but I had a similar problem when I first got my S3 up and running. Certain channels (all of the local HDs) were blocked--signal strength 0. One CSR actually tried to tell me that local HD channels were not a part of my package! It took several escalating calls to Comcast. I eventually called the 'executive assistant' which someone recommended to me on this forum (215-665-1700). The Executive Assistant sent out a competent tech who had the problem fixed in 5 minutes.