When I deactivated my plugin and reactivated it, the following error popped up: Plugin could not be activated because it triggered a fatal error. The weird thing is that the debug frame that should show the errors causing the plugin activation to fail was blank. There were no errors in my php_error log either.

This is the second time this lunacy had me baffled. Everytime it takes me at least 30 minutes to figure out why it happens. When $wpdb->show_errors(); is defined in your plugin, it won’t activate. Not sure why, but it just won’t activate. Removing the line allows you to reactivate normally.