I had this happen once on a client's PC.
First: Can you FTP?
Open a Command Prompt.
Type FTP
You should get an "FTP>" prompt.
Type "open ftp.mozilla.org"
type "ls"
type "cd" followed by whatever directory you need to get into their public releases
type "bin" or "binary"
type "get" followed by the filename (shown by "ls") of their latest release
when that's done, type "close"
then type "bye"
then type "exit"
After I type "ls" at the FTP prompt, I get "Not connected.", followed by a FTP> blinking cursor.