FTP auto disconnecting users

I'm having this little problem with an FTP that I'm running. Users build models and upload the files to my server. The files are binary. The problem that I'm getting is that the users will get disconnected after almost every transfer (even if they have a queued file).

What could be the problem?


I am using G6FTP with Windows XP-Pro

The logs are not helpful---it goes like this:

"finished uploading(or downloading) XXXXXXX (xxx[time used for process] - xxxKb [size of file] - x Kb/s [Av speed]"

Next entry is:

USER xxxx
PASS ******
Disconnected

Even though the sender has files queued up, the next entry after that is client logging on again.

The puzzling thing is that not every user is having this problem and they're using different clients.

I have DHCP, so I have a *no-ip* type of name and I'm using port 21. People have been using both PASV and non PASV to connect.

I'm thinking its the client, but people who have been connecting to be before are having this problem. I have switched ISPs recently, could that be it?


Max.