Too lagging in Quil server in last 2 days.
First, make sure you are running Grand Fantasia in Administrative Mode, and make sure it is allowed through your firewall and antivirus, and that you have disabled UAC (User Account Control).
Open GF, run a full scan from the launcher, and play a bit, and see if that helps.
If it doesn't, your next step would have to be to turn off other running programs (like Chrome, Akami NetSession, Skype, Pando Media Booster...etc) that run with heavy bandwith. Chrome has been known to give GF issues, while the others just sap bandwith like crazy. You'll want to really turn off what you aren't using. Unfortunately, Grand Fantasia has a lot of data loss after time. All your bandwith is really needed. Even I have fantastic internet and still disconnect because of this reason. Shut your client every 2 hours and it should prevent further data loss, and less lag and disconnecting issues.
A program like GameBooster
will also help shut off unnecessary process and give you better performance overall.
If you're still having issues, update your drivers, defrag your computer, and update your computer as well. You should also uninstall anything you aren't using as well.
If after all this you're still having connectivity issues, contact your ISP to make sure that you don't have any blocks on your end. It doesn't sound like it, but it never hurts to check (and it's free).
I hope this helps you, and happy gaming.