Have you called Comcast about the connectivity issues? I was having problems with connections dropping and packet loss. I called them, they sent a tech out who replaced a bad wire connecting to the building. Apparently others in the building had the same problem, but I was the only one who had a tech come out.
When damaged, coax (and POTS-based DSL for that matter) are both susceptible to environmental changes, so a cool-down in the evening can significantly change the characteristics of the wire, higher levels of humidity don't help either.
In other words, yet another reason fiber to the premises is superior.
