This error happens to everyone who has a Windows 7 format. When you select a server, double click on one and just wait, after that notice pops-up it should stop the lagging and put you in the server you selected. If not, you should be automatically moved to the server you're closest to(Does it to me sometimes). If you double click on a server and it starts to lag, press Enter and you should be moved into the Inventory or Weapon Shop in the server you selected. This also works for me. Try either option and it should work. NHN USA has to fix this error for all Window 7 format users. If neither options work, please reply back with your response.
Have a happy killing spree!
~Evl