It has to be a Steam game:
If you still have this problem, go to your KSP folder and search for "settings.cfg". Delete this file and set a new start option
( Steam library -> right klick on KSP -> select the option at the bottom (dont know what it means in english ) -> select the Tab "general" -> click on "set startoption" )
write in "LC_ALL=C %command%" (without these charter ["] )
if it wont work at all, I cant help sorry If it works much fun while playing