I installed the latest MySQL and perl-DBD-MySQL from Rawhide. These place files in /etc/ld.so.conf.d containing "/usr/lib/mysql". However, libraries in that directory are not subsequently added to the cache, as revealed by "ldconfig -v". Running ldd against the mysql.so from perl-DBD-MySQL shows that it can't find libmysqlclient.so.14. I strace'd ldconfig and found that it never referenced /etc/ld.so.conf.d. If I run ldconfig with /usr/lib/mysql included on the command line, my Perl scripts (and in particular, my bugzilla installation) work again.
Make sure include /etc/ld.so.conf.d/*.conf is in your /etc/ld.so.conf Guess you haven't merged /etc/ld.so.conf.rpmnew with /etc/ld.so.conf during some upgrade. FC3 glibc edits this file automatically, but FC2 does not. Anyway, during any install you should scan .rpmnew files and check what needs updating always, otherwise you can end up with not fully functioning system.