Crisis averted! ??
The problem was that when I was updating wp-config.php, the damn auto-correct features in Apple’s notepad turned my single-quote mark into an apostrophe (which PHP didn’t like). Curses Apple!
For others, I highly recommend submitting your php file to a syntax checker. That picked out the problem right away.
@b — Thanks for the suggestion about the multisite, I’ll look into it.
