My webserver needed virtual ftp user support. Well the proftpd package on FC4 didn't have native mysql support. So we need to rebuild the package.
First download the latest package. Then we need to run the rpmbuild command. So type:
rpmbuild --rebuild --with mysql proftpd-1.2.10-4.src.rpm
NOTE: if you are using yum be sure to add proftpd to your exclude list.