I'm seeing very strange behavior at the irb prompt with ruby 1.9.1  
(2009-01-06 patchlevel-5000 trunk 21356) [i386-darwin9.6.0]

I can enter some accented characters (such as ), but not other  
characters (such as ,  and ). Some of those other characters  
echo as ?, while others are ignored.

If I disable readline, then everything works OK.