follow these commands:
etc/init.d/proftpd stop
yum remove proftpd
yum install proftpd
cp /etc/pam.d/proftpd /etc/pam.d/proftpd_orig
cat /dev/null > /etc/pam.d/proftpd
*say yes to overide
nano /etc/pam.d/proftpd
add this to /etc/pam.d/proftpd
#%PAM-1.0
auth required pam_unix.so nullok
account required pam_unix.so
session required pam_unix.so
chkconfig --levels 235 proftpd on
/etc/init.d/proftpd start
after i did this, it was ok. my problem was that i was very slow