Certain channels freeze over digital signal for extended periods of time

I am a Comcast customer in Nashville, TN. I am having a reoccuring issue in which MSNBC in my area freezes when viewing from the digital signal but is fine when watching on the analog side. I have reported this issue to no avail and I am positive that it is not an equipment issue because I have multiple boxes and the problem is intermittent (yesterday the signal was lost from 9am-11am and then returned and worked normally for the rest of the day. Other days the signal is out for most of the day.) This is standard and not an HD issue.