on RHEL 5 IBM, I build mod_security from source and when trying to load it from htttpd, see really strange thing

scenario 1: run apachectl start from conf dir, fails:
[root <at> aw-ecweb01s conf]# ../bin/apachectl start
Syntax error on line 5 of /opt/IBMIHS/conf/mod_security.conf:
API module structure `security2_module' in file /usr/lib/httpd/modules/mod_security2.so is garbled - perhaps this is not an Apache module DSO?
scenario 2: run apachectl start from bin dir, httpd starts, but seems mod_security is not loaded:
 [root <at> aw-ecweb01s conf]# cd ../bin
[root <at> aw-ecweb01s bin]# apachectl start

questions:
 1. why the starting dir make such difference?
  2. how do i know whether mod_security is loaded? I have debug logs but seems do not see any log being generated.

thanks!