Problem

File names with Non-ASCII Charecters will not open in LumenRT 2015

Solution

LumenRT 2016 ( Not Yet Released as of 15/03/2016 ) will be able to handle European and Asian Charecters in the file name.  

Note that Bentley LumenRT 2015 SELECT version can still handle Non-ASCII Characters in Level Names, Material Names ect. It does this by stripping the Non-ASCII Charecters from the name.