|ISP issues, apparently. I didn't believe them, cos that's what they said last time they blocked port 80.|
Oh well. Thanks to Kris and Eli for their help troubleshooting from without the network while I was inside (everything worked fine inside). We didn't accomplish much other than determine pretty conclusively that AT&T was dicking around with something.
I think I'll run a full and complete server backup tonight, just in case. Shit like this spooks me...