I'm not sure if it's because I didn't realize I had to set the plugin into safe mode, or because I'm still running WP 2.9.2. I upgraded the plugin from 3.0.4 to 3.0.9 through the admin interface. After the upgrade, s2Member disappeared from the admin menu, and some or all of the settings appear to no longer be taking effect [such as login logo].
If it's any help, I can still see all the former settings in the DB as ' ws_plugin__s2member_options'.
How can I get it back to normal?