Reminder to self (and anyone else) before upgrading your installation of wordpress to the latest it is a good idea to upgrade and turn off all plugins (or as many as possible) and re-enable them after the upgrade.
I did a “one button” upgrade (nice tool of DreamHost’s) of all my WordPress blogs to 2.8, without deactivating the plugins. For two of the blogs everything was silky smooth, however the other two…
Fatal error: Call to undefined method WordPress_Module::_weak_escape() in ~/wp-includes/wp-db.php on line 487
and nothing else.
Fortunately I had a mirror of the old site right before the update so I was able to restore that and examine the plugins. Only three were common to both blogs, so I turned them off, then recopied the new modified files back. Sure enough everything worked fine.
A quick upgrade of the plugin to the latest version and everything is good as new. Now to start playing with WP2.8