The solution for this is pretty simple.
Note: this guide shows how to do the process, at the bottom you will find the latest version of the patches needed for this guide to work (This guide corresponds to the updates up to May 15th, if you scroll down you will find the latest files, you have to update EVERY SINGLE RPT that you don't see in your folder but see in this guide, any question about it just let me know )
In your explorer (I used Google Chrome) paste this:
This will download a file each.
Now go to the patches folder and paste these files you downloaded in it.
By default, the patches folder is located at C:\Program Files (x86)\Gravity\Ragnarok Online 2\Patches
Go to the game root folder and look for a file called Version (Is a DAT file) open it with notepad (If you don't know how to do this: right click the file, press Open with... instead of Open and select notepad).
You will find that inside it says something like this (It could say 17, also, the work around is the same):
Change it into:
Save the file.
Launch the game and have fun
May 21th Update
If your client is up to date besides the patch that was released last night, you will need to do this process again with just one file, the link for it is the following:
On the Version.DAT instead of changing it to what the guide shows now should be:
Edited by Ryogure, 22 May 2013 - 07:23 AM.