The instructions on Apache.org say:
In httpd.conf, you will need to have the following lines (preferably in their respective context):
LoadModule log_forensic_module modules/mod_log_forensic.so
LoadModule unique_id_module modules/mod_unique_id.so
Are these already installed? I need to see what is really happening to my request.
mod_log_forensic is included in most distribution packages of Apache and comes with the source tarball download, but if you compile Apache 2.x.x from source, you need to add --enable-log-forensic and --enable-unique-id to the configure line.