Well, that's exactly what I wound up doing. I expunged the whole site
from SP and IIS. I then extended my existing good site, removed all
existing doc lib documents and re-uploaded them. After all that,
things seem to work fine.
Have any of you experts seen a site (or maybe just a document
library) go corrupt like that? At least, I assume that it was a
corruption. I can't think of what else it could have been. The doc
lib name/URL didn't contain any illegal, or otherwise suspect,
characters that might have caused SP's processing engine to choke.