I've finally got a shadow FOB Drupal site up at home so that I can play with the latest Drupal stuff and hopefully improve things around here. The key configuration blunder in my 4-hour setup extravaganza? My new Apache 2 installation didn't have mod_rewrite turned on…
The diagnosis was a pain. See, Drupal has a bunch of rewrites it sticks into its .htaccess file, of all places. These rewrites are necessary to get Drupal to work in most installations. Of course, they're all conditionalized on the installation of mod_rewrite.
The end result is that Drupal silently fails to rewrite its URLs properly if mod_rewrite is not installed. If the rewrites hadn't been conditionalized, they presumably would have crashed. Then I would have noticed that I needed to do some more Apache config, and it would have taken me minutes instead of hours of screwing around.
Bleah. If you need some feature to work, explicitly fail if it's not available. There are worse things than a crash.