FTP Folder Error, Windows cannot access this folder

Hey guys,

Im having some problems this morning with the creation of my FTP

I can successfully get to the site internally, but I can not
externally. The external user seems to be able to reach the server, and
when entering the username and password they receive a message as

""FTP Folder Error
Windows cannot access this folder. Make sure that you typed the file
name correctly and that you have permission to access the folder.

The connection with the server was reset.""

I dont think this is a firewall issue? but maybe. I have gone back to
all the folders Im wanting the users to access and they have full
control over these... I have unchecked allow anonomous connections, as
I need the users to login... dont know if thats right...

Im using IIS 6.0 on a Windows 2003 server.

Thanks in advance.