I chucked it all and went back to 300 baud. Now it works.

Just put an init string to default your 56k modem to 28.8. Try at&v90=0. Also, try updating your winmodem firmware. That's often the issue. Thanks for calling AT&T Worldnet!

Fuckity what?

Winmodems, the first true hardware hurdle for all Linux all the time for me. I ended up stuck with a 14.4 modem for ages, because faster hardware modems were almost completely replaced by winmodems in the UK. They sucked so much. Ah, demon internet in 1995.