I'm using a WordPress network installation on my server and the awesome Domain Mapping plugin. We are releasing new magazines every second month. The Maintenance Mode Plugin is installed on all sites in the network, but the maintenance mode is only used on the blogs that aren't yet released to the public.
When not logged in to the site or the network, I now see the following php error instead of the maintenance site by the plugin. This happens only on the blogs in my network where the plugin is set to maintenance mode "on":
Fatal error: Call to undefined function is_rtl() in /home/myserver/public_html/wp-includes/general-template.php on line 2102
Any suggestions or ideas? It worked fine before WordPress 3.3.