ANSWER:

1 – you need to know what is been block firts. download “process monitor” from sys internal (microsoft).

2 – on the program, select only “show network activities” (a button on the bar on the upper left)

3 – check the packets and find the FTP ones. (server1.domain.com:12345 -> server2.domain.com:21)

4 – righ click on the name of the process and select include to add the process that is running the ftp.

5 – test the ftp tranfer with the firewall and without it.

6 – compare both data. it should be a port blocked by the firewall. you should open that port between both PC.

by Edward from http://serverfault.com/questions/390666