Lacking suggestions, I obliterated all my files and reinstalled everything.
It works now, but I still have zero clue what might have caused a sudden failure to connect when I had a 2-week string of successes.
If anyone bothers to read this that has an answer... I used Navicat to attempt a dump of some of my DB tables. While it appeared to leave a dump file, it wouldn't source it when I tried to a few minutes later. Any suggestions there on dumping individual tables?
In the meantime, I am resorting to frequent db backups in its entirety.