You're likely behind a Cable/DSL router and/or a firewall. The first thing to try is to turn on PASV mode in your FTP client. Your FTP client should have some checkbox or similar that enables this. This fixes most users' problems. Some users have also reported that updating the firmware in their routers has ended their troubles, so you may want to check if there's an update available for yours. If you're still having problems, you probably have a firewall that is blocking connections to our server. This could be in your cable/DSL router, or in firewall software you have installed on your computer. Since this involves software or hardware on your side, the OCF staff will, unfortunately, only be able to offer rather limited assistance. You'll just have to fiddle with the settings, especially with ones mentioning "trusted site", "allow connections to", or something along those lines. You may also find it useful to note that the FTP service is on port 21.
Regular FTP allows potential eavesdroppers on the network to capture both your authentication information (username and password) and the data you are transferring. However, our FTP server supports an extension called SafeTP that provides a layer of encryption around regular FTP. To take advantage of it, you need to download and install the SafeTP client (available for Windows only). Note that another (better) option is to use the SSH Secure File Transfer client that comes with SSH Secure Shell. If you have a CalNet ID, you may find it easier to download this from UCB Workstation Support Services.