If you happen to use non-ASCII characters in a ruby file within your rails app, say a controller, library, database seeds, etc, you might have the invalid multibyte char (US-ASCII) error thrown at you by ruby 1.9.x. This is something you’re bound to experience if you’re developing an app that is localized in a language that utilizes non-ASCII characters and you’re not using the i18n libraries of rails to define your strings. The solution is very easy and feels almost magical:
Put this line of code on top of all scripts that raise the error. Unfortunately there seems to be no way to deal with it on application level with a single entry. It’s Ruby legacy, but perhaps it should be considered as a Rails default for future versions.