UPDATE, 11:15 p.m.: People beginning to report their Comcast Internet service is back up.
Twitter's currently lighting up like a working Internet modem with reports from all over of Comcast Internet outages. Bonnie Sashin reports from Brookline that when she called the Comcast customer-service number, she got a recording telling her to go online for service, which, um, hey, Comcast, maybe you're not getting the idea?
It's some sort of screwup with Comcast's DNS servers (basically, the directories the network uses to figure out how to connect you to universalhub.com or smuttyporn.com or whatever) - and is affecting the East Coast at least as far south as Virginia. The more technically minded out there suggest that if you know how to change your DNS settings, change them to 188.8.131.52 and 184.108.40.206 (Google) or 220.127.116.11 and 18.104.22.168 (OpenDNS).