I'm on AT&T (U-Verse), though not a 4chan user (I actually don't even know how to test that the /b/ board is working or not, though I'd be interested in trying).

A few months ago I couldn't access drudgereport.com and a few others sites reliably for several days. It worked via vpn from work, and on the neighbor's Comcast connection, but those of us in my area on U-Verse were getting server connection resets.

I don't attribute it to network filtering (Hanlon's razor as mentioned in another comment ... and I work for a large telecom ... sometimes the tubes need to be snaked).

Though we ruled out DNS -- I use OpenDNS and we tested the Comcast connections set up to use OpenDNS which worked fine. There was at least one other person outside of my home state that experienced the same problem on U-Verse as well.