FTP service spontaneously stopped working!?

[jacksondesignco]

FTP was working just great...and now it died for no reason. :O

We have successfully been using ftp service with a new XServe 2 (Base Station 802.11n as gateway) for about a month. But, possibly following the latest firmware update that was run on the base station a few weeks ago, the ftp service just stopped working.

FTP works within the network if I connect via Cyberduck using the internal server address. But, to connect from the outside using the IP that is offered from within Base Station—the way we've done this successfully for a whole month—Cyberduck will spin and spin and never even see the network much less attempt to authenticate. Crazy.

• I have done a hard reset on Base Station. No change.
• I have unplugged and reset cable modem multiple times. No change.
• The ISP has confirmed that ports 20 and 21 are still open. Nothing unusual from their end.
• I've used ServerAdmin multiple times to stop & start ftp service, restart server, etc. No effect.
• Here's a curious detail: from the server I can go to whatismyipaddress.com, and it correctly sees the Base-Station-issued IP that I am trying to connect via ftp from the outside. Hmm.

Any experience from someone who can help isolate this issue? I'll admit, it appears to be a Base Station issue (maybe. likely.) since I can connect ftp from within the network. And, I am about 60-70% certain the latest firmware update was run near the time it spontaneously stopped working. But, ftp had been working. Not sure what is different now or why resetting things is not fixing anything.

Thoughts? Thanks in advance!
Greg