In running Drupal on apache 2.2, too many files are opened by the webserver. For some reason the files aren't closing after the page is served. When a page is accessed again, a new set of files are opened (and remain open). These open files accumulate until apache refuses to open any more. It's as if the "process" isn't terminating, so none of its file handles know to close.
Strangeness #1: This site (code and database) served on an ssl connection over apache 1.3 runs fine, without keeping files open.
Strangeness #2: This site, with just the code and default module settings seems to run fine over apache 2.2.
suspect features and modules: apache mod_rewrite, secure_login (which uses a redirect)