Bugs with FreeBSD 5.2.1

A have DirectAdmin installed on FreeBSD 5.2.1 and there are some strange bugs with IP management a ProFTPd.
For example, yesterday I got an error "Address xxx.xxx.xxx.xxx:21 in used by 'ProFTPd'" starting ProFTPd.
Where can I get manual for updating my Directadmin and ProFTPd?
Sorry for my stupid question, but I couldn't find any documentation on http://directadmin.com

Of cause, there wasn't any proftpd proccesses running.
I tried to find 21 port using 'netstat', 'lsof' commands.

If you are 100% sure nothing is bound to port 21 then I dont know whats causing the error but the problem isnt FreeBSD 5.2.1 as I have had proftpd with DA running fine on this setup.

And what about any documentation? I want to try to update DA and proftpd...