My forum is in Taiwan , many users use Chinese characters as their login name (column : USER_LOGIN_NAME) in UBB5 (It allowed special characters in login name long time ago . After UBB6 , it is disabled) , after migrating to UBB7 , these users cannot login.

How to solve it ?

English is not my native language. I try my best to express my thought precisely. I hope you understand what I mean. If any misunderstanding results from culture gaps, I apologize first.