So, I ate a magic bean (didn't know what it was at the time, but evidently it's from Thaumcraft), and the server kicked me off and wouldn't let me back on. Tried a couple of times, got "internal server error" and "disconnected: end of stream" messages, respectively.
Got a brief message about radiation poisoning before I got kicked off, so I thought maybe I needed to wait a while for that condition to go away or some such thing, but it's been an hour or two and no luck (now getting "end of stream" message consistently). Pinged the server and got a response, but suspect it's something server-side at this point regardless.