Ugh, I don't really know what to say...
Reinstall, let it update. After it's done try to run from loader, if it's not working then go to your Rohan folder and delete the Game Guard folder and all the .set files you can find. Start from rohanclient.exe and see if it works. If you gets to ID and PASS screen, close it and run loader.
Now it should work.
If the above steps ain't working, you can also try to run Loader as administrator; also make sure your drivers are updated and that you're allowing Rohan through windows firewall & antivirus. Also make sure you clean your caché and everything. I'd recommend CCleaner or Glary Utilities 4, free and easy to use.
Not working? Send ticket here and they will help yah out.