You may get this message when connecting to a server for following reasons:

• You may have typed a wrong hostname on Login dialog.
• Your domain name is new and is not fully distributed to DNS servers yet.
• Connection was blocked by firewall. Please refer to FAQ.
• Problem with DNS server.
• Common mistake is to enter full URL (e.g. ftp://ftp.example.com) as hostname on Login dialog instead of actual hostname (e.g. ftp.example.com).