This makes sense because the "Network" tab in "Configure Player" (emplode) does not appear when connected via ethernet.

Easiest way to fix this would be to configure the IP when connected via USB or setup HiJack so that you have one set of Network settings for "@Home" and another for "@work" so you don't have to change them that often. (Looking back now, it would have been nice to have @Home use DHCP and @work use an assigned IP - but I've switched jobs now so it's mute.)