said by Rick5:this Is specific to Comcast for me which would seem to rule out your list.
 
Ahhh... OK.
I just logged in to comcast . com using Firefox, and went to Tools | Options | Privacy | Show cookies
I see that many of the cookies comcast uses are session cookies. One cookie is set to expire in 30 minutes, the remaining cookies are set to expire as soon as they are set, i.e., they expire immediately.
Based upon that, it looks like the issue is on the comcast side of things.