I think I have also upated glibc already and it is glibc-2.5-58.el5_6.4 now. For the time being, I am not managing Asterisk via GUI. Hence, I will give one or two more days to observe if there are any other side-effects before restoration.
Thanks for your kind advice. Of course, I won't remove glibc. For me, GUI is always not a stable media to manage my Asterisk. What I am concerned about is the impact on other areas. With your opinion, I'll wait and see.
As far as I know, Asterisk 1.8 does not have ISO. You have to compile from it scratch. What Zalman can help is to install CentOS 5.6 image but it is a very good start.
SMS and VoIP using USB modem in Asterisk is one of the examples that cannot be updated just via YUM. Another one is OBiAPP integration with Asterisk. We have to install some 3rd party packages separtely to make them work.
For updating the new version of Asterisk, I just need to checkout the latest version via svn and then run make && make install. That is all.
For Asterisk 10.0.0, I am looking forward to the official release other than the version of release candidate. Once they are ready, I may try it together with CentOS 6.0 or 6.1