For people still dealing with the problem, looking at /var/log/messages will tell you exactly where it bugs. I've commented that include line and everything is ok.
On my version: rpm -qa | grep proftpd shows :
psa-proftpd-xinetd-1.3.6-8.el6.art.x86_64
psa-proftpd-1.3.6-8.el6.art.x86_64