I'm running a Debian Squeeze box with Redmine 1.1.2, Apache and Passenger. After a system update that upgraded the rubygems package to version 1.8.x, Redmine was broken with the following error message:
undefined method `name' for "rubygems-update":String
This is due to an incompatibility between Redmine and recent Rubygems versions. The problem can be fixed by downgrading rubygems to a lower version, in my case 1.3.7. You can check the current version with
$ gem --version
1.8.15
To downgrade rubygems, you need to make gem install an older version of rubygems-update. As root, run:
$ gem install rubygems-update --version=1.3.7
...
$ REALLY_GEM_UPDATE_SYSTEM=1 gem update --system 1.3.7
...
$ gem --version
1.3.7
That's it, after restarting Apache (or whatever your webserver is), Redmine should work again.
(Of course, a better alternative would be to set up a more recent version of Redmine on a more up-to-date operating sytem. See my Ubuntu / Redmine / Nginx / Mongrel / Supervisord blogpost for a howto on setting up Redmine on Ubuntu.)