Check out the patch notes for the v19 Winter Mischief update here: http://maplestory2.nexon.net/en/news/article/55464/winter-mischief-v19
Try running maplestory 2 through the nexon launcher and no other way.
This means, don't run Maplestory 2.exe. Run nexon launcher as administrator and select maplestory 2 on the games tab and hit "play"
Let me know the results.
1) Make sure Nexon Launcher is exited. Check your start menu programs on the bottom right.
2) Run Nexon Launcher as administrator
3) Hit play on MS2 through the Nexon launcher
3a) If you run MS2 through any other method you are bound to get error messages.
WOW! you are genius!!! but it dosen't work sorry still 400/600ping. It's nexon problem. not mine. Just look at the bug report and tech support.