How do I prevent a "Page not found" error for URLs containing non-Latin characters?
Consider trying the Transliteration module. Here is a quote from its project page:


  ... it takes Unicode text and tries to represent it in US-ASCII characters (universally displayable, unaccented characters) by attempting to transliterate the pronunciation expressed by the text in some other writing system to Roman letters.


As a sample, it transforms an URL like mydomain.com/последние-новости-в-Украине-и-мире in something like mydoamin/poslednie-novosti-v-Ukraine-i-mire.

Other modules that might help to solve this question:


Global Redirect.
Pathauto.