Updating Passenger
Updating the passenger gem is a bit of a pain. Its dead easy to just to the gem update and forget to do the other stuff you need to do, especially if you update lots of gems at the same time.
Anyhow after updating passenger be sure to run passenger-install-apache2-module as root. Follow the instructions and update the passenger config (in/etc/apache2/other/passenger.conf on my work box)