A You may encounter this error when you try to download from an FTP server using either Internet Explorer 3 or 4. FTP servers are usually configured to return textual error information when your connection fails. In this case, Internet Explorer has received an error from the FTP server, but is unable to understand why the connection failed. The most probable cause is that the server has reached its anonymous FTP connections limit. Another possible cause is that Internet Explorer cannot use passive mode to transfer files from the server, and does not currently support normal mode. In passive mode, file transfers are initiated by the client software (your browser); in normal mode the server connects to the client. Currently the only solutions are to try connecting at different times, or to use alternative FTP programs to download from the server.

IE4 may generate this less than helpful error message when connecting to an FTP server