He's gone now. I think he was a sinus headache, and ibuprofen + entex (aka, pseudoephedrine++) seem to have driven him away.
The funny thing about Tontor is that it didn't actually hurt all that much -- it wasn't a migraine, and I've had worse headaches, honestly -- it was just this thudding pain that made it impossible to concentrate enough to actually do anything. I managed to write a dozen lines of code, but they were about as simple as can be.
Anyway, it just lead to some general ruminations on the very burst-y nature of productivity in programming and heck, knowledge work in general. I wonder how prevalent that is across professions and types of work?