Can you provide more information then just DC. What version are you running? What are you trying to import? What programs are you using? We need more information to be able to help.
Having the same issue - when users go into the boss, everything is fine. When reaching the final body, they will either have major UI issues such as disappearing faces, disappearing inventories, then will shortly disconnect aftwards. Relogging doesn't help, but closing out the client completely and restarting works. Any ideas?