Cannot open directory (ftp_choose_dir.php)

[bsn]

I found where is problem!
I run
tcpdump -i lo -n -nn
and I see this
21:09:54.787138 IP6 ::1.33991 > ::1.21: Flags [S], seq 773365646, win 32752, options [mss 16376,sackOK,TS val 45778022 ecr 0,[|tcp]>
21:09:54.787171 IP6 ::1.21 > ::1.33991: Flags [R.], seq 0, ack 773365647, win 0, length 0
Why IP6?
I don't use ipv6.
I have changed /etc/proftpd/proftpd.conf
UseIPv6 off -> UseIPv6 on
Then
service proftpd restart
And now ftp_choose_dir.php work correctly.
Maybe this is not the best solution, but it worked.

Sorry for my english