Problem
After upgrading your server to use rvm and Ruby 1.9 you get the following error when you are trying to access certain parts of your redmine installation:

passenger ArgumentError (invalid byte sequence in US-ASCII)

Solution
If you follow the instruction posted here, you can add the following to your redmine’s “RAILS_ROOT/config/initializers/string_encodings.rb”:

Encoding.default_external = 'UTF-8'

and restart your application