had the same problem, all active plugins where disabled for the upgrade (2.8.4a->2.9.2), and enabled again after.
set define(‘WP_DEBUG’, true); in config and video plugin was the first to ‘notice’.
Disabled video plugin (0.71 at the time) and problem was solved. Must check if we really need that plugin and/or if the new version 0.73 ‘plays nice’.
