For a large number of machines behind a firewall it may be simplest to run a personal proxy within the firewall through which all client machines will transfer keyblocks.

If you suspect that your computer is being blocked by a firewall, it can be helpful to see how your web browser is configured. If you can figure out how it manages to talk freely with the world then perhaps the same strategy can be used for the client. For instance, from within Netscape you can select "Options" / "Network Preferences" and see if it is configured to communicate through a firewall. Often, you can just take this information and plug it directly into the client and everything will work perfectly.