So Rails 2.2 has come out recently, and it's touting some nice features. These include internationalization (i18n) and thread safety - the thread safety aspect isn't so great for C Ruby, but is excelled for JRuby which uses a different threading system.
There is one problem though, and that's for anybody (like us) who is using ruby-gettext, which is an i18n gem for Ruby and Rails for doing translations. The problem is that gettext depends on plenty of the little things in Rails that were not thread-safe, and are consequently no longer there. If you even attempt to load the Rails environment with the gettext gem included (by doing something like script/server, or a rake task), it will blow up in your face.
The solution right now is not that cool. You've got a few options:
1) Revert to 2.1.2. Kinda sucks, since we're using JRuby for our app and I was looking forward to the fancy schmancy new stuff.
2) Fix the gettext issues yourself. Really sucks. While like a good FOSS boy I should be all over this one, time is my most limited resource and well, it has to go to things that either keep me fed or keep me sane.
3) Wait for the people behind ruby-gettext to fix it. Also sucks, because we have no idea when that will happen.
4) Rip out all the gettext stuff and replace it with Rails' new i18n stuff. Probably the best solution, however this takes more time than 1) and so is not on the immediate horizon.
So if you're using gettext, remember not to update to Rails 2.2+ without first ditching gettext. Or if you were thinking of using gettext, I'd recommend saying "screw that" and going with Rails built-in stuff.
UDPATE(Jan. 11/09): We have gone through and removed the gettext stuff from our app. Fortunately we weren't dependent on any gettext-related tools, so this was not a difficult task, just replace all the _ calls with t() calls (can by done easily with Netbeans using refactoring tools), and some configuration details. Was pretty simple fortunately.