Flyff is known to me to install correctly.
However, this app will not run properly due to the fact that it cannot run the patcher client.
When opened, it gives an dialouge box saying that the patcher client did not run, but will execute once you press ok. When ok is pressed, the application hangs.
Further development will be needed for this to work properly, but untill then, dont install this program, its just waisted space.