1) Uninstall l2, delete everything from l2 directory, leave no trace of l2 on your computer...
2) Install l2 in the new directory named Lineage II ofcoarse
3) Make sure you have the new l2.exe and the wildcard files found on this site http://fyyre.ivory-tower.de/ (im not too sure what exactly you need, but u need l2.exe and another one called wild card) However u can change l2.bin into a l2.exe, but it doesnt work for me so dl l2.exe directly off that site i gave you
4) Make sure the server ur trying to connect actually works with no one else having a problem
5) If you still get the error, perhapes your anti virus or fire wall or something you installed reccently is blocking it, its highly unlikely but u never know.. always think opposite of what youd expect to find, as in think of EVERYTHING youve done between the time it stopped working, and the time it did work.
Usually a full reinstallment with clean files works 100% for me and others, but if thats not the case, the problem is within your computer, a possible virus or somthing thats not allowing you to play that causes a crit error.
Hope this helps.