Take a look at one of the unmodified sample input files that come with DirectRT. Try to run it--does it run ok? If so, make a change to it now that you have changed the regional settings. Does it still work?

I ask because changing the regional settings will not fix a file that has been previously saved under a different regional setting that uses semi-colons instead of commas. However once you change those semi-colons back to commas (e.g., using a search and replace in a text editor) then you should be fine from then on.