FTP Problem using IE and non-standard port

Local Login works fine, Cant access via Web

[ConfusedServer]

I am setting up an FTP server using Win 2000 Server, and it is working ok locally, but when I go to access it via the web, i get a 500 error, command not understood. I have the ports forwarded in the router, and the browser (IE6) appears to 'see' that there is actually something there, but wont let me in. I know this because if I enter a BS folder that doesnt exist, I get a different error.

The syntax I'm using to get access is:

ftp://x.x.x.x:port/folder/

it then asks me for the user name/password like it does locally, but then the error rather than the folder.

This is only happening when I specify the non-standard port (using this to obscure the writeable folder), if I allow it to default with 21, I can access the read only portion of the site just as I can locally.

I know this all points to the port forwarding, but I've checked and double checked it, and not having problems with other things such as VNC, Terminal Services, Etc. Glitch in the router firmware? It's a USR 802.11g Wireless Turbo Router.

Any help would be greatly appreciated.

[tedster]

Wish I had some words of encouragement - but we were doing this last year and it worked for us. Any security in place that might account for the trouble?