problems with utf8 + String class

Ruby String methods assume the string is a single byte per character,
which as you know, is not the case with unicode strings. therefore a
multibyte character in your string is going to throw everything off.
Such is the nature of Ruby.

as a starting point, i suggest you check out:

http://wiki.rubyonrails.org/rails/pages/HowToUseUnicodeStrings
http://julik.textdriven.com/svn/tools/rails_plugins/unicode_hacks

Chris