Ugh.. Site to Site problems..

[Switch-NL]

i'm also having troubles fxp-ing to a friend of mine.
when i'm not using my router+firewall i can easily fxp files to him. but whenever i'm behind my router, it immediately says it can't send files
(1) PWD
(1) 257 "/SOMEFOLDER" is current directory.
(1) TYPE A
(1) 200 Type set to A.
(1) PORT xxx,xx,xxx,xxx,9,62
(1) 200 Port command successful.
(1) LIST
(1) 150 Opening data connection for directory list.
(1) 425 Cannot open data connection (10060).
Transfer Failed: SOMEMP3
Transfer Failed!