I noticed that my RVM-handled irb in OS X (Mountain Lion) didn't like Norwegian characters today. So instead of an 'ø', I got '\U+FFC3\U+FFB8' during entry, and nothing afterwards. Like so:
Not really satisfactory. After googling: "os x irb unicode characters rvm" I found the answer on stackoverflow.
My adapted solution was this:
So now I can do:
(Not quite sure why the '--verify-downloads 1' part is needed, but it did the trick.)