Comcast seems to have wireless (wifi) set top boxes, it sounds like that's what you have.

I seem to think I had a discussion before with someone who mentioned signal problems and some equipment that may have been set up wrong, that made it sound like there may have been interference and conflicts arising from the equipment that was in a house. That person said they were going to have their son check it out. Was that you?

What remains is to work it through with Comcast and if they're not successful, hire a home PC/networking technician to review and test your equipment. I hope they're successful. Good luck.