When I upgraded the User Online plugin (wp-useronline) a short while ago, I got a Fatal Error:
Fatal error: Call to undefined method scbOptions::get_key() in …/wp-content/plugins/wp-useronline/admin.php on line 56
I looked on Google and found the WordPress Support page http://wordpress.org/support/topic/396809 and renamed the plugin folder “wp-useronline” to “xwp-useronline”.
I then went to the Plugins page on my Dashboard, and then re-installed the plugin (by searching for “wp-useronline”).
Everything working now 🙂
Last week, the company I use to host my website upgraded from PHP 5.2 to PHP 5.3. When this happened, my web site went completely blank :-(. I couldn’t get anything to appear, and couldn’t even log in to the dashboard.
However, after enabled PHP errors, I discovered that the “WordPress Automatic Upgrade” plugin was causing the problem.
I renamed the appropriate plugin folder through the host’s admin site, and then my site worked!! 🙂
Looking at the plugin website (http://wordpress.org/extend/plugins/wordpress-automatic-upgrade/”>http://wordpress.org/extend/plugins/wordpress-automatic-upgrade/, it appears that the plugin is only compatible up to WordPress 2.7.1, not 2.9.1!!!
Hope this helps other WordPress users 🙂
UPDATE (19/04/2017) The plugin website above is no longer active, as from WordPress 3.7+ minor upgrades are done automatically, so the plugin is no longer relevant.