This morning at around 7:30AM EST my site started throwing 500 errors. I moved the plugin folder out of the way and the site loaded. I put the plugin folder back and started moving each plugin one at a time and when I moved the wpmudev-updates plugin the site returned to normal. I see on the other sites that are working that it now has a message that stuff has moved to The Hub. Not sure if that could be part of the issue. The server is running PHP 5.2.14 from 9/5/12 (I am asking the sysadmin to upgrade since this is causing issues with the ability to use some plugins).