Pixelation issues on some channels in ATL area

For a couple of weeks now, I've had lots of pixelation on certain channels (to the point where it's unwatchable) and some channels out altogether. Comcast have "sent a signal" to my box to no avail.

It seems to come and go. For example, I could be watching channel 124 (Fox Soccer Channel) and it will be fine for an hour and then become unwatchable.

For the channels that are totally out, channels either side are fine so I'm assuming this is a frequency problem (and I'm also assuming that the bad channels are on the same frequency)

Is there any chance this is a problem on my side? I really don't want to lose a day's pay to wait for Comcast to come out and say my signal is OK.

I have basic + digital + HBO + HSI. The HSI has been fine.