SFTP Limited Availability

At my location we have two internal networks. I have installed OpenSSH 4.4 on a server on one of those networks and the only change I made was for it to use port 21 instead of port 22, since port 21 was available and getting ports opened here is a production in itself. If I SFTP to that server from a computer on that same network, it works fine. If I attempt to SFTP to that server from a computer on the other network, I get the following error:

Using SSH Protocol version 2. (it sits at this line for quite a bit of time, then these errors appear.)

Network error: Connection reset by peer
Unable to initialize SFTP: '8 square boxes here then' t (sftp not enabled?)
Can't establish connection --> domainnamehere:21 @ date/time here (122-1)

Any ideas?