At sensr.net we provide free FTP logins for people with network cameras. A common problem is that IP cameras, like the DCS-920, can't always do DNS. This means that the camera can have problems reaching our servers, say f3.sensr.net, since it can't find the IP address for the FTP server.
The best way to fix this is to set a DNS server in your camera's network settings page. You can either dig out the DNS settings for your ISP, or you can simply use 208.67.222.222 and 208.67.220.220. These servers are the DNS servers from OpenDNS, another favorite startup of mine.
Eventually we'll have better realtime support to help you debug your FTP server settings. In the meantime, check those DNS server settings!
