FTP problem

[gottimd]

When I update the NAFL with my reports, I use an FTP program. If I select to upload too many files, it seems like the FTP craps out on me, and gives me this message:

  PASV
 Connection Closed. 
java.net.SocketException: Connection reset
 java.lang.NullPointerException 

So I have to select a small group of files to upload at a time, or else the FTP will give me the above error and disconnect.

This only seems to happen at work. When I am at home and I am logged into my home network, the upload is slower but I can select all of the files without this hangup.

Any ideas why this happens?