[Xitami] ftp issues(I'm Stumped)

[xitami@lists.xitami.org]

I recently helped a friend install Xitami 2.5c2 on a pc running XP. Everything was working perfectly until yesterday. Users trying to connect to his ftp service are presented with this error:

Connecting to 83.70.231.6:21
Connected to 83.70.231.6:21 in 0.170244 seconds, Waiting for Server Response

Failed to receive response after connect
Host type (1): Automatic Detect

I double checked his network and router configuration. Everything is ok there. He can access the http and ftp servers locally. It's just access from the net that is receiving the error. After prodding him a little further it turns out he enabled XP's built in firewall(not sure why he did this, his router uses NAT) right before his server went south. Ah, hah, I figured, easy fix. He insists on keeping his firewall enabled, so I had him configure it
to allow HTTP an FTP to no avail. After that failed I had him disable the firewall, still nothing. Users are still receiving the same error. I was positive XP's firewall was the issue. Does anyone know what could be causing this. I've been using xitami for four years on my own machine, but in no way claim to be an expert. I'm stumped. 

Thanks in advance for any help!