Thanks for reporting. Are you sure that first download was successful? The file that Ladybug downloads is the same file as what you get in Radiance. Just to make sure I updated the file again. I also added a new check to the component so in case Radiance is already installed it copies the file from Radiance folder instead of downloading it.
for some reason it use to download a version of gendaymtx.exe that was only 1Ko! (maybe windows 8.1 protection? but in fact it’s a good thing to avoid hacking if your exe file was hacked in your dropbox)