Well, almost.

I managed to trip over the MySQL documentation that discussed the particular solution to my problem. Apparently the standard PHP MySQL client cannot handle the new hashing for passwords...lost you already, didn't I?

Essentially, I had to add a key to the MySQL config file telling it to use the old password hashing algorithm, and that let me get the PHP sites working!

This is now running on MySQL v4! Sweet. I did a backup on v3, immediate shutdown, started v4, restored, and now she's purring along.

The almost part is that I'm running the 32-bit version, but want to run the 64-bit version. Why not, right? Tonight I'll stop the database server, copy the databases, and start the 64-bit. What can go wrong?