Petru's suggestion to ad -DEAPI is a good one; however, there is
more you can do to diagnose this.
1) Run "apachectl configtest" and see if the syntax of your
httpd.conf file is ok.
2)Look at the error_log for more detailed information. My guess
is that you are running on a platform that requires you to run
"ldconfig" whenever you add additional libraries to the system.
Did you just install Postgres? If so, you linked against the PG
libraries; if you did not re-run ldconfig and add the PG libs to the
ld.so cache, then starting Apache will fail.