> 17:39:39.841313 ftp.netbsd.org.ftp > dhcp30-19-61.berklee.net.49280: R
> 1435768395:1435768395(0) win 0
> ^C
> 8330 packets received by filter
> 0 packets dropped by kernel
>
> There's that big "R" packet just after the anonymous login.
>
> At first we thought that this had to do with reverse DNS lookups, but
> now that's been fixed and the problem persists.
>
> Other ftp sites seem to work just fine. It's just a problem with
> ftp.netbsd.org (so, as a result the network guys say it's MY problem!).

could you try ftp.pl.netbsd.org?

to check if it happens with any NetBSD ftpd based server or just
ftp.netbsd.org