So I've compared MD5 of whole 2 clients, 1 working 1 not, and here are the results.

Files MISSING in broken client:
"MD5","FBBD58C1EFA6B928579C6F9C3897787D","C:\Games\LineageII EU\system\Frost\frostStatic.log"    irrelevant
"MD5","C9E90DC4017584D022971ABC0EEDB7E2","C:\Games\LineageII EU\system\chatfilter.ini"    not sure, prolly irrelevant
"MD5","7CED59EE4F53FFE083048E9E69A3AA36","C:\Games\LineageII EU\system\l2.log"  irrelevant I guess
"MD5","9D43EA9A28638DE052BA2C123058DCE9","C:\Games\LineageII EU\system\Localization.ini"    might be the issue
"MD5","7EC50465D2920E0AD6A0A261DBF43C8F","C:\Games\LineageII EU\system\Option.ini"   missing or should be created on successful launch
"MD5","E218E468803828ABE878E169E8655F50","C:\Games\LineageII EU\system\TTFontInfo.ini"   no idea
"MD5","D74F9F694D9D226E72ADFC5460612C56","C:\Games\LineageII EU\system\User.ini"   missing or should be created on successful launch
"MD5","0544E02A65FBF1865489C3DE803195D6","C:\Games\LineageII EU\system\WindowsInfo.ini"

The only MD5 different file was
"MD5","CF23F90FBD58B8E447A3ECB5A8BC4704","C:\Games\LineageII EU\system\Frost\launcherUpdater.log"   which is irrelevant