@repanzer: The symptoms are most likely due to a poor connection between the cable box and Comcast's network, usually in or near your home.
Troubleshoot by checking all connectors for corrosion and tightness, and by looking for damaged coax cable. Running the cable through a surge protector, a defective splitter, or too many splitters can cause signal problems as well. If there is an amplifier in the line make sure it's getting power. You might also try unplugging the cable box/DVR/digital adapter power cord for a minute or so.
If you can't find the problem call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/ and insist they send a tech out to identify the cause and correct it.
If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast cable box/DVR/digital adapter or anything outside your home, you shouldn't be charged.
Hi repanzer. Thanks for visiting and posting on the Xfinity Forums. Apologies for our delay in getting to you. If you still need assistance with the Syfy channel pixelating, I can help. Please let us know if you require any further assistance.