So, a basic/minimal install of CentOS 5.6 and bugzilla I'm greeted with a non-helpful "failed to connect" page and a /var/log/httpd/error_log message of:
[Tue Apr 19 13:10:15 2011] [error] [client xx.xx.xx.xx] [Tue Apr 19 13:10:15 2011] index.cgi: Use of uninitialized value in substitution (s///) at (eval 42) line 44.
[Tue Apr 19 13:10:15 2011] [error] [client xx.xx.xx.xx] [Tue Apr 19 13:10:15 2011] index.cgi: Use of uninitialized value in concatenation (.) or string at Bugzilla/CGI.pm line 312.
Following google search links proves useless (which is not often the case).
I added all of the interesting perl modules that bugzilla may want. Modules like perl-DateTime, perl-List-MoreUtils, perl-PatchReader, perl-HTML-Scrubber, perl-Template-GD, perl-GD-Graph, perl-Chart and ImageMagick-perl (plus their dependencies). /usr/share/bugzilla/checksetup.pl ran without issue, produced no error, fixed and rebuilt etc... still the error... paying a tiny bit more attention to the area around line 312 in Bugzilla/CGI.pm, I finally notice https redirection code... Wait, bugzilla defaults to requiring https but does not check for https... finally problem solved. The solution is just to install "mod_ssl".