FTP oddity

[Blazej Sawionek <B.Sawionek@elka.pw.edu.pl>]

I have two hosts, running bo and hamm respectively.
I can't ftp (telnet either) from hamm to bo. 
The session goes as:
$ ftp bo
Connected to bo.my.domain.name
421 Service not available, remote server has closed connection
ftp>
...

If I ping from hamm it sees bo.

Additionally I _can_ ftp from hamm to any place in the world and i
also can ftp to bo from different hosts (all to which I have access).

I can ftp from bo to hamm, but when I try to put long files it just
hangs after having transmitted approx. 2MB.

Any ideas?

Blazej