I just found this error on my WPMu installation "Cannot redeclare wp_unregister_globals() (" and the only thing I had experimented with recently is WP_Super_Cache. Anyone else having a similar issue? I don't want to assume it is WP_Super_cache, but when I deleted the plugin the site came back fine. So, any expertise out there that might be able to confirm or disconfirm this theory?