Do you get an Access denied error when doing it in a browser window?
If so do the following and see if it helps out:
Go to th Control Panel , then to Internet Options.
Select the Advanced Tab
Under the Browsing area there is an option to "Enable folder view for ftp sites"
Uncheck this option and then try your ftp site again.
Hope this helps!, This was an issue i have seen with ftp's and usernames in IE 5.x.