Problem occurs when you set up an iPlanet Reverse Proxy Server to run with a Domino Server and leave all the iPlanet Portal Profile settings as the defaults. Then you setup a DOLS-enabled database on the Domino server, editing the Offline Config Document in the database at least once and saving the default settings.
From a client, log into the iPlanet Proxy Server, then load the DOLS-enabled database through the proxy server. The database loads, but the DOLS download control (which normally says "Go Offline") does not load in the web control frame.
Workaround
Open the iPlanet Portal Management Profile and remove window.location.pathname from the "Rewrite Javascript System Variables" setting. Then restart the iPlanet server.