Verified answer

You should try loading it again, and if that doesn't work, try restarting your computer. The same thing happened to me earlier today, restarting my computer helped me, and should probably help you too. I hope it does. ;X

Well... I found this on the Flyff site:

"Dear Flyff Fans,

Over the weekend some of you may have experienced technical difficulties when trying to log into and play Flyff. The issue was related to the routers, most likely a result of maintenance performed by our server providers last week.

We have been notified that the issue is resolved so you can now return to your normal gaming experience. For those of you who experienced technical difficulties over the weekend, we sincerely apologize for the inconvenience.

As a way of saying “Thank You” to our fans for your continued support, we are currently planning a special event that should take place soon. We’ll keep you posted.

Thank you,

Gala-Net and the Flyff Team"

Its probably fixed now. Try logging in again. If its something else, I suppose you'll have to reinstall.

Happy Gaming :)

Sometimes the only way is to download the client from the official website.