Problem with KL_DIRECTORY.exists on Windows

I'm trying to build a windows binary of my swete application.  When I
run the application, KL_DIRECTORY.exists returns false even through
the directory exists.  i.e.

directory: KL_DIRECTORY

create directory.make (directory_name)
if not directory.exists then
  directory.create_directory
end

The execution fails with a permissions error at
directory.create_directory even though this statement should never be
executed because a directory with directory_name already exists on
disk. Same result replacing .exists with .is_readable

It works fine on linux. Am I using KL_DIRECTORY incorrectly?

Neal