1) Edit /etc/hosts, replace the old one in the first settings "203.80.89.135 s2hkbntel.net s21.hkbntel.net" by the following line. Others remain unchanged.
What have you done? Install asterisk 1.8.2? just save a copy of the new one and then recover the old conf files. Try again. There have been changes in the confi but not that many. For me, I just use my 1.6 config files directly on 1.8 asterisk. No change of any config files.