The archive stuff is magically working again. I suspect (given the debugging I did, before giving up and using another method) that it was my fault, not some strange, arcane, Blogger problem.
Anyway, the cool Java drop-down menu (along with other, more “normal” options) can be found here, courtesy of Phil Ringnalda, with discussion on the general topic of reformatting archive files into a more aesthetic form to be found here.