Are you having a problem accessing an FTP site on a client PC on a network behind Microsoft Forefront Threat Management Gateway (TMG) or an ISA Server (502 Proxy Error)? if so, this article is for you, and explains how to overcome the problem.
When a user tries to connect to an FTP site from a PC where Internet Explorer is set to use a proxy server, they may receive an error message from the proxy server:
“Network Access Message: The Page cannot be displayed”. Technical information section: “Error Code: 502 Proxy Error. The login request was denied. The logon account might have been disabled or logon information might have changed. Log on again to verify that the information was typed correctly. If the problem continues, report the problem to the administrator of the Internet server you are requesting (12015)”.
To connect successfully to the FTP site, do the following;
1) When Internet Explorer returns “The Page cannot be displayed” page, go to the Page menu and click Open FTP site in Windows Explorer.
2) A window appears requesting the FTP username and password.
3) Enter FTP credentials and the user should be able to logon successfully.