FTP issue with windows2003?

I'm a web developer, and in the last month I've noticed gradual slowness

in FTP connections to a couple of different w2k3 servers turn into a

totally crippling inability to connect.

While I have no problem whatsoever FTPing to a number of other servers

-- including what is, I think, a W2k3 server running a third-party FTP

server software -- these three Windows servers have a lot of trouble

keeping a persistent connection. I get lots of PORT errors, listing

errors, and the logs also show a lots of disconnects and reconnects.

Is this an issue that's arisen because of a Windows update? Or some

other factor that would hit three otherwise unrelated servers all at the

same time?

Thanks.