I'm going to try jemplode later today to see if I get any more information.
If you do, make sure to scare up the latest JAR file from Mike Schrag, his most recent ones are the most compatible with the Central. There's a thread on the Empeg BBS about it where I talk about how I got hierarchical playlists running on the Central with it.
You said that the unit replies to pings and also replies to HTTP queries, so we know that the ethernet adapter is working. So i'd say the next thing is to look at the Emplode options and see if any of those are off. And of course try Jemplode like you said. What version of emplode are you running?