Bulletproof FTP Server problems

I got this error when trying to receive an fxp:

226 File received ok.
RETR test.r01
550 Cannot store on server.
ABOR
226 ABOR command successful.
Transfer Failed!

I got someone else to try and he got a different error:

[R] LIST -al
[R] 451 Failed: Cannot build data connection..
[R] LIST
[R] 550 List failed. No port specified.
[R] List Error
[R] PORT 212,242,110,3,19,157
[R] 200 Port command successful.

I have ADSL and modem/router Topcom Xplorer 871BT


Sometimes i only get a bit of a file before it aborts and start on the next thing in the queue..

Anyone know what the problem is? And how to fix it?
Regular upload works fine btw

I was able to fix the last problem...people are able to connect and start a fxp, but it keeps stopping and just idle...could that have something to do with portforwarding on the router?

I have a slot called private port, but i didnt put anything there because i opened many ports, the ports 5000-6000...