netjukebox

you need to grant permissions to netjukebox. if you're running on a unix machine, try this:

cd /top/of/media/path
find . -type d -exec chmod o+w {} \;

what this will do is look at each of the files in the tree specified by /top/of/media/path (in your case it looks like /media/disk3, but really it ...

also, I know that vlc is running on the http remote control interface, because navigating to http://localhost:5123 brings up the web player (albeit with nothing to play)

Marvelous bit of software you've got going here. I've just been having difficulty getting playback working using VLC (videoLAN?)

I'm running on a mac, and go through the following procedure:
from the web interface, config -> player profile
-name: localhost
-check videoLan
-auto-detect: server ...