For reasons that I have yet to discover, my outbound connection to the Internet appears to have been down between the times listed in the title.
As I have said before, my connection is less than “professional grade”, i.e. “don’t do this at home”.
If I find a cause, I will update.
I apologize for the incovenience.

Found a MONDO huge problem with mysqldump in MySQL 5.0.15 — it locked the tables. Totally.
I backup the database by taking a dump 4 times a day, 12 hours apart on two machines.
The Web server machine, where I was testing MySQL 5.0.15 prior to the production upgrade, is using the version mysqldump that shipped with that.
I need to read the docs and disable the table locks.